Equalization (if needed) is gear and room oriented. With Shannon--Nyquist you always get the perfect data required to perfectly recreate the signal you want to capture.Ok, understand that in practice equalization is under Nuquist requirements so don’t need infinite accuracy. Then the information lost is under audible threshold or at least is lower than the perturbation to the signal added by room modes and reflections…
But some time ago a member gave some advices to equalization: under 400 Hz, only 0 to -6 dB and Q factor <= 5
Is this based more in acoustics than in digital analysis of the signal?
PEQ is about coming as close to that in your room, with your equipment. Personally I don't use EQ. I use measuring equipment to position stuff as best as I can in my environment (and I have had the luxury to pick good environments).