ISKCON which advocates Achintya-Bheda-Abheda, believes that the impersonal Brahman is an expansion of the personal Brahman i.e. Krishna as you can see in the following web article:
The Vedic texts give the analogy of the sun regarding the personal and impersonal aspect of the Absolute truth. The sun has form as a celestial globe and is formless in its widespread effulgence. Similarly, God or Supreme Brahman has form as the Supreme Person, Krishna, and is formless as the all-pervading effulgence known as impersonal Brahman. Just as the sun globe is the source of the sunlight, Krishna is the source of the impersonal Brahman (as is confirmed in the Gita (14.27) and other Vedic literatures).
So I'm assuming this is the view of Achintya-Bheda-Abheda. Advaitins, on the other hand, believe that the impersonal Brahman i.e. Nirguna Brahman is the original Brahman and people under Maya perceive it as personal i.e. Saguna Brahman.
Goswami Tulsidas, who belongs to the Ramanandi Vaishnava sect, which advocates Vishishtadvaita, writes in the Ramcharitmanas that Brahman is originally formless and takes a form only for the sake of His devotees:
“Though as a woman I am not qualified to hear it, I am Your servant in thought, word and deed. Saints do not withhold even an esoteric truth wherever they find a man smitten with agony, and therefore qualified to receive it. I ask You with a heart sore distressed; be gracious enough to narrate the story of the Lord of Raghus. First tell me after a mature thought what makes the unqualified Brahma assume a qualified form. Then, my lord, relate the story of Sri Rama’s descent, and tell me next the charming exploits of His childhood. Then let me know how He wedded Janaka’s daughter, Sita, and the fault for which He had to renounce His father’s kingdom later on. Then describe the innumerable deeds performed by Him while He lived in the forest; and further tell me, my lord, how He killed Ravana. Then relate, O blissful Sankara, all the numerous sports that were enacted by Him after his coronation. (Spoken by Mother Parvati to Lord Shiva in the Bal-Khanda of the Ramcharitmanas)
However, the Ramanandi Sampradaya's Vishishtadvaita philosophy may differ slighty from the Vishishtadvaita philosophy preached by Sri Vaishnavas.
So I wish to know what are the views of Sri Vaishnavas and Nimbarkites on the notion of Brahman being originally formless/impersonal/Nirakara? Do they agree with Gaudiya Vaishnavas that Nirakara Brahman is simply an expansion of Sri Hari? Or do they agree with Tulsidas that Brahman is originally without any form but for the ease of Jivas, takes a form so they be able to comprehend Him?