I think this is a theory of advaita or shaivite schools.I dont think other dualistic schools have Nirvikalpa (No-form) concept.I would like to hear from them.
Nirvikalpa is "no form" as per definition here. But Nirvikalpa according to Bhakti path is loosing the "I" and all thoughts in your Ishtadeva. When that state is permanent, that is Sahaja Samadhi. Moksha in Bhakti path means being Atmaroop and worshipping/serving your Ishtadeva.
Regards,
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