Bhakti Rasāmṛta Sindhu (1.2.295) says,

sevā-sādhaka-rūpeṇa siddha-rūpeṇa cātra hi
tad-bhāva-lipsunā kāryā vraja-lokānusārataḥ

The two mentions of “form” in the statement (siddha-rūpeṇa & sādhaka-rūpeṇa) are in instrumental grammatical case, acting as instruments for the subject, sevā. So, this statement is not directly about the practitioner’s body/form. It is about two forms of our bhakti-practice (seva).

All forms of sādhana are based on emulation of a desired objective. Rāgānugā, however, is more specific than conventional bhakti-sādhanain its intentions and objectives. Therefore, some of what it needs to emulate will be impractical or impossible to us. For example, how well could a male practitioner emulate the behavior of the female gopīs, like dancing with Krishna, decorating themselves for him, etc.? How would anyone emulate the paternal affection, which involves educating and correcting Krishna? Or how would we emulate the friendly affection which involves playing games with Krishna?

Śrī Rūpa addresses this problem by introducing the concept that a practitioner can do siddha-rūpeṇa seva – emulation via imagination and visualization of being in forms and circumstances that enable these sorts of interactions with Krishna.

He says that a Rāgānugā Practitioner should perform their practice in both practical and imaginary format (“sevā sādhaka-rūpeṇa siddha-rūpeṇa ca”). For example a person inspired by paternal love might practically emulate feeding a deity, constructing a home for it, etc. and by singing songs that express paternal affection, but some aspects of paternal love, like educating and correcting the child are much more easily and engrossingly done in an “idealized form” (siddha-rūpeṇa) – by visualization, imagination, etc.

Although this statement is not directly about a practitioner’s body, indirectly our practices determine our next birth. As Nārada explained to Pracinabarhi in the Fourth Canto, the mental state generates the physical form – but it takes some time for the effects to manifest, so they occur most fully when the physical body changes (“reincarnation”). So the visualised body is the root of our real form – especially in our next birth. Ideally our next birth would be in Krishna-loka, in a form that is ideal for interacting with him and his community.