Various Forms of Nimbarka

Nimbarka is Sudarshan Chakra - a very important Shakti and aspect of BhagavAn

In Leela Kshetra of Bhagavan :

1. In MAdhurya Ras, Nimbarka is Ranga Devi In the same Leela kshetra , Ranga Devi in turn is lusture of Radha's limbs (Krishna is the tree, Radha the creeper around it, Sakhis and Manjaris are the Radha-creeper's leaves, branches, flower buds...) and similarly he is Radha's nose ring (sakhis being aspects of Radha's personality) 
2. In Sakhya Ras he is Shri Tosha Sakha
3. In shanta-vAtsalya ras he is Gushara the cow
4. In shanta ras he is the stick to herd the cows 

** Madhurya includes all aspects of all other rasas. The devotee's sthAyi bhav is fixed, but KRshNa can temporarily make him/her act otherwise.

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MORAL  : Vrindavan is ONE SOUL expanded in a variety of forms to enhance the bliss of KRshNa. The entire Golok DhAm combined is KRshNa. (Well so is entire Swetadweeep that includes Vaikuntha ... down to Material world)

This is dvaita-advaita philosophy. This is also shuddha-advaita.

Nimbarka is simultaneously (a) one with (b) different from KRshNa. This is achintya-bheda-abheda. (its achintya i.e. inconceivable, since its not that simple)