As in Wayland yes. X does have color correction stuff, which is the most important part.
uh, kinda not really? I mean, you can calibrate your screen to sRGB, if you calibrate it to anything else, every non managed app will completely and utterly break
what have you used? If you set, say DCI-P3 (not display p3 which uses a similar transfer to 2.2) the issues become evident due to the different transfers that it is quite off.
if you used something like display p3, then due to the similar transfer, only gamut changes which is a lot harder to notice at a glance