There is no difference between thinking of Srimati Radharani and Kṛṣṇa, and personally associating with Them.

Srila Prabhupada - "Radharani's mind, senses and body are steeped in love for Kṛṣṇa. She is Kṛṣṇa’s own energy, and She helps Him in His pastimes. Śrīmatī Rādhārāṇī is as fully spiritual as Kṛṣṇa. 

No one should consider Her to be material. She is definitely not like the conditioned souls, who have material bodies, gross and subtle, covered by material senses. 

She is all-spiritual, and both Her body and Her mind are of the same spiritual embodiment. 

Because Her body is spiritual, Her senses are also spiritual. Thus Her body, mind and senses fully shine in love of Kṛṣṇa. 

She is the personified hlādinī-śakti (the pleasure-giving energy of the Lord’s internal potency), and therefore She is the only source of enjoyment for Śrī Kṛṣṇa. 

Śrī Kṛṣṇa cannot enjoy anything that is internally different from Him.Therefore Rādhā and Śrī Kṛṣṇa are identical. 

The sandhinī portion of Śrī Kṛṣṇa’s internal potency has manifested the all-attractive form of Śrī Kṛṣṇa, and the same internal potency, in the hlādinī feature, has presented Śrīmatī Rādhārāṇī, who is the attraction for the all-attractive. 

No one can match Śrīmatī Rādhārāṇī in the transcendental pastimes of Śrī Kṛṣṇa." (Caitanya Caritamrita Adi 4.71, Translation and Purport)

Caitanya Caritamrita Madhya 23.68, Translation - "The transcendental goddess Śrīmatī Rādhārāṇī is the direct counterpart of Lord Śrī Kṛṣṇa. She is the central figure for all the goddesses of fortune. She possesses all the attraction to attract the all-attractive Personality of Godhead. She is the primeval internal potency of the Lord."

Srila Prabhupada - "Kṛṣṇa and Rādhārāṇī are both transcendentally qualified, and both of Them attract one another. Yet in that transcendental attraction, Rādhārāṇī is greater than Kṛṣṇa, for the attractiveness of Rādhārāṇī is the transcendental taste in conjugal love. Similarly, there are transcendental tastes in servitude, friendship and other relationships with Kṛṣṇa." (Teachings of Lord Caitanya, Chapter 14, Purport)

Srila Prabhupada - "When Kṛṣṇa left Vṛndāvana for Mathurā, the gopīs became most dejected and spent the rest of their lives simply crying in separation from Kṛṣṇa. This means that in one sense they were never actually separated from Kṛṣṇa. There is no difference between thinking of Kṛṣṇa and associating with Him. 

Rather, vipralambha-sevā, thinking of Kṛṣṇa in separation, as Śrī Caitanya Mahāprabhu did, is far better than serving Kṛṣṇa directly. 

Thus of all the devotees who have developed unalloyed devotional love for Kṛṣṇa, the gopīs are most exalted, and out of all these exalted gopīs, Śrīmatī Rādhārāṇī is the highest. 

No one can excel the devotional service of Śrīmatī Rādhārāṇī. 

Indeed, even Kṛṣṇa cannot understand the attitude of Śrīmatī Rādhārāṇī; therefore He took Her position and appeared as Śrī Caitanya Mahāprabhu, just to understand Her transcendental feelings. 

In this way Śrīla Rūpa Gosvāmī gradually concludes that Śrīmatī Rādhārāṇī is the most exalted devotee of Kṛṣṇa and that Her kuṇḍa (lake), Śrī Rādhā-kuṇḍa, is the most exalted place." (Nectar of Instruction 10, Purport)

Srila Prabhupada - "Of the many objects of favored delight and of all the lovable damsels of Vrajabhūmi, Śrīmatī Rādhārāṇī is certainly the most treasured object of Kṛṣṇa's love. And, in every respect, Her divine kuṇḍa is described by great sages as similarly dear to Him. 

Undoubtedly Rādhā-kuṇḍa is very rarely attained even by the great devotees; therefore it is even more difficult for ordinary devotees to attain. If one simply bathes once within those holy waters, one's pure love of Kṛṣṇa is fully aroused. 

Why is Rādhā-kuṇḍa so exalted? 

The lake is so exalted because it belongs to Śrīmatī Rādhārāṇī, who is the most beloved object of Śrī Kṛṣṇa. Among all the gopīs, She is the most beloved. 

Similarly, Her lake, Śrī Rādhā-kuṇḍa, is also described by great sages as the lake that is as dear to Kṛṣṇa as Rādhā Herself. 

Indeed, Kṛṣṇa's love for Rādhā-kuṇḍa and Śrīmatī Rādhārāṇī is the same in all respects. 

Rādhā-kuṇḍa is very rarely attained, even by great personalities fully engaged in devotional service, not to speak of ordinary devotees who are only engaged in the practice of vaidhī bhakti." (Nectar of Instruction 11, Translation and Purport)

Srila Prabhupada - "Lord Caitanya exhibited the mode of Śrīmatī Rādhārāṇī when She was contacted from Dvārakā by Śrī Kṛṣṇa. Such transcendental love is not possible for any common man; therefore one should not imitate the highest perfectional stage exhibited by Caitanya Mahāprabhu. 

If, however, one desires to be in that association, he may follow in the footsteps of the gopīs. In the Padma Purāṇa it is stated that just as Rādhārāṇī is dear to Kṛṣṇa, similarly the kuṇḍa known as Rādhākuṇḍa is also very dear to Him. 

Rādhārāṇī is the only gopī who is dearer to Kṛṣṇa than all the other gopīs. 

In Śrīmad-Bhāgavatam Canto 10 Chapter 30 Text 28 it is also stated that Rādhārāṇī and the gopīs render the highest perfectional loving service to the Lord and that the Lord is so pleased with them that He does not wish to leave the company of Śrīmatī Rādhārāṇī." (Teachings of Lord Caitanya, Chapter 30) 

Srila Prabhupada - "As Kṛṣṇa is the highest emblem of spiritual perfection, so Rādhārāṇī is the highest emblem of that spiritual pleasure potency by which Kṛṣṇa is satisfied. Since Kṛṣṇa is unlimited, in order to satisfy Him Rādhārāṇī is also unlimited. Kṛṣṇa is satisfied just by seeing Rādhārāṇī, but Rādhārāṇī expands Herself in such a way that Kṛṣṇa desires to enjoy Her more. 

Because Kṛṣṇa was unable to estimate the pleasure potency of Rādhārāṇī, He decided to accept the role of Rādhārāṇī, and that combination is Śrī Caitanya Mahāprabhu." (Teachings of Lord Caitanya, Chapter 31)

Caitanya Caritamrta Adi 4.76, Translation - "Just as the fountainhead, Lord Kṛṣṇa, is the cause of all incarnations, so Śrī Rādhā is the cause of all these consorts."

Caitanya Caritamrita Adi 4.82, Translation - "Rādhā is the one who gives pleasure to Govinda, and She is also the enchantress of Govinda. She is the be-all and end-all of Govinda, and the crest jewel of all His consorts."

Caitanya Caritamrta Adi 4.83, Translation - "The transcendental goddess Śrīmatī Rādhārāṇī is the direct counterpart of Lord Śrī Kṛṣṇa. She is the central figure for all the goddesses of fortune. She possesses all the attractiveness to attract the all-attractive Personality of Godhead. She is the primeval internal potency of the Lord."

Caitanya Caritamrta Adi 4.96, Translation - "Śrī Rādhā is the full power, and Lord Kṛṣṇa is the possessor of full power. The two are not different, as evidenced by the revealed scriptures. The attitude of Śrīmatī Rādhārāṇī is the highest perfection of conjugal love."

Srila Prabhupada -"Lord Caitanya’s heart was full of the feelings of Śrīmatī Rādhārāṇī, and His appearance resembled Hers. 

Svarūpa Dāmodara has explained His attitude as rādhā-bhāva-mūrti, the attitude of Rādhārāṇī. One who engages in sense gratification on the material platform can hardly understand rādhā-bhāva, but one who is freed from the demands of sense gratification can understand it. 

Rādhā-bhāva must be understood from the Gosvāmīs, those who are actually controllers of the senses. 

From such authorized sources it is to be known that the attitude of Śrīmatī Rādhārāṇī is the highest perfection of conjugal love, which is the highest of the five transcendental mellows, and it is the complete perfection of love of Kṛṣṇa. In the loving affairs of Rādhā and Kṛṣṇa, Rādhārāṇī is the āśraya feature and Kṛṣṇa the viṣaya." (Caitanya Caritamrta Adi 4.106, Purport)

Srila Prabhupada - "Viṣaya and āśraya are two very significant words relating to the reciprocation between Kṛṣṇa and His devotee. The devotee is called the āśraya, and his beloved, Kṛṣṇa, is the viṣaya. Different ingredients are involved in the exchange of love between the āśraya and viṣaya, which are known as vibhāva, anubhāva, sāttvika and vyabhicārī. 

Vibhāva is divided into the two categories ālambana and uddīpana. Ālambana may be further divided into āśraya and viṣaya. In the loving affairs of Rādhā and Kṛṣṇa, Rādhārāṇī is the āśraya feature and Kṛṣṇa the viṣaya. The transcendental consciousness of the Lord tells Him, 

'I am Kṛṣṇa, and I experience pleasure as the viṣaya. The pleasure enjoyed by Rādhārāṇī, the āśraya, is many times greater than the pleasure I feel.'

Therefore, to feel the pleasure of the āśraya category, Lord Kṛṣṇa appeared as Śrī Caitanya Mahāprabhu." (Caitanya Caritamrta Adi 4.135, Purport)

Srila Prabhupada - "Among the gopīs, Śrīmatī Rādhikā is the foremost. She surpasses all in beauty, in good qualities, in good fortune and, above all, in love. Among all the gopīs, Śrīmatī Rādhārāṇī is the most exalted. She is the most beautiful, the most qualified and, above all, the greatest lover of Kṛṣṇa." (Caitanya Caritamrta Adi 4.214, Translation and Purport)

Srila Prabhupada - "Rādhā is the beloved consort of Kṛṣṇa, and She is the wealth of His life. Without Her, the gopīs cannot give Him pleasure. Radharani is the chief damsel of Vraja in love with Govinda, the Supreme Personality of Godhead, Śrī Kṛṣṇa." (Caitanya Caritamrta Adi 4.218, Translation)

Srila Prabhupada - "The fact is that both Kṛṣṇa and Lord Caitanya are the original Personality of Godhead. No one should try to eliminate Lord Caitanya from Śrī Kṛṣṇa. In His form of Śrī Kṛṣṇa, He is the supreme enjoyer, and in His form of Lord Caitanya, He is the supreme enjoyed. 

No one can be more superexcellently attractive than Śrī Kṛṣṇa, and but for Śrī Kṛṣṇa, no one can enjoy the supreme form of devotion, Śrīmatī Rādhārāṇī. But for Śrī Kṛṣṇa, all Viṣṇu forms are lacking this ability. This is explained in the description of Govinda in Caitanya-caritāmṛta. 

There it is said that Śrīmatī Rādhārāṇī is the only personality who can infuse Śrī Kṛṣṇa with transcendental pleasure. Thus Śrīmatī Rādhārāṇī is the chief damsel of Vraja in love with Govinda, the Supreme Personality of Godhead, Śrī Kṛṣṇa." (Teachings of Lord Caitanya, Chapter 32)