The question is too generic since there are multiple ways of building this system. Different scopes have difference spring arrangements. The means of how turret stems contact the tube vary. The overall amount of adjustment that the turrets can have is often guardbanded with stops put in that prevent excessive pressure on the erector tube, etc.
With PRB, you have to be really careful with how you interpret the optics info there. It is often misleading due to being either over simplified or just wrong.
If you plan to spin the turrets a lot, none of the $100 scopes will do the trick. The erector tube is not supposed to bump the inside of the maintube since there should be a limiter in action prior to that. On cheap scopes it might do something like that, but not on any decent ones.
Being at the very end of vertical adjustment can effect horizontal adjustment and vice versa, but you have to keep in mind that there are other effects at the end of the adjustment. For example, for many scopes, if you adjust that far, you need to re-adjust the parallax.
ILya