What is the minimum resolution of an xbox360 or newer or a ps4?
Estimated 600x800
Many games now use dynamic resolutions, which is a good thing. Most of the PS4 runs at 900p to 1080p. The XBox One is a step down, most of it runs at 720p to 900p, but also gives 1080p. The minimum for the XBox One was even "significantly below 720p" for Titanfall 2 due to the very aggressive dynamic scaling, so to achieve 60 FPS at all costs. The last-gen consoles (PS3 & XBox 360) were aiming for 720p.
With the PS4, you can set the resolution to a maximum of 480p, but what it looks like with Xbox, I don't know exactly
The PS4 pro and especially the One X get away better.
Yes, of course. I only dealt with the generations mentioned in the question.