T2 can be disabled to allow booting from unsigned OSes or external media but it can’t be disabled for its hardware controller functions. It is the disk controller, audio processor, image signal processor for the camera and iirc some power management functions as well, and other things I’ve forgotten and am too lazy to look up.
re: the problems people are having, like many issues it seems to affect a relatively small number of users. Sometimes a machine swap solves it, sometimes it makes no difference. There are likely multiple failure modes. It often seems to be related to attached Thunderbolt devices and sleep modes, at least when I was following the thread.
As is typical with these threads, there are hundreds of posts from the usual spewers of all things Apple-hate—who don’t even own the machine—yet will tell you over and over how horrible it is, that it’s a hardware flaw that affects every machine, how Apple has lost their way, Tim Cook only cares about profit, Apple only cares about iToys and hates the Mac, etc. ad nauseam.