@Project Dharma
Veere PaarBrahma/PaarShiva concept is very much part of part of Hinduism and predates even Buddhism. Infact there are many sects within Hinduism which had similar outlook. Just take a look at: concept of ancient Avudaiyarkoil temple in Tamil Nadu.
Now coming to text you quoted by Shri Guru Nanak.
The Simritis, Shastras and Vedas describe many mysteries, but I don't recognise even one of them; O Sword-wielder God! All this I write, with your blessings, is not what I know but what you have shown me."
Let me quote you a similar text from Shri Bhagvad Geeta. That might give you new insight on the line said by Shri Guru Nanak:
यावानर्थ उदपाने सर्वतः संप्लुतोदके।
तावान्सर्वेषु वेदेषु ब्राह्मणस्य विजानतः।।2.46।।
Rough tranlsation(Sanskrit Rakshasas(analogous to Grammar Nazis) here can correct the translation further):
A Self Realized Brahmana(ie who achieved Nirvana/Moksha) has that much utility in all the Vedas as a man has in a well when there is a flood all around.
Similar thoughts were expressed by other Gurus/Swamis(in Sanatana Dharma) who were born later. The kind o criticism which we see by Guru Nanak towards superflous practices in Hinduism is not new. Same criticism existed before and infact even is expressed in Bhagvad Geeta. It even predates Bhagvad Geeta from times jostling between Vedic Karma Kanda(ritualistic) and later development of Vedic Janan Kanda(Knowledge based) or Upanishads.
Infact Shri Govind or Shri Krishna himself indirectly refers himself as formless one in a quote from Bhagvad Geeta:
avajānanti māṁ mūḍhā
mānuṣīṁ tanum āśritam
paraṁ bhāvam ajānanto
mama bhūta-maheśvaram
Resorting to a human form, foolish people insult me, not knowing my supreme nature as the overlord of all beings.