As for your wheel wobble I know there is wobble on the MK1 at around th 70 mph mark but you just drive through it to 75 mph and it is gone or you ease off a little . I have seen lots of posts concerning this and the many and varied solutions offered but none ever work completely ! If you take a MK1 NA stock as it came out of the factory it would have this . Then we start messing with them changing wheels and suspension adding body kits and the like . Poor thing does not stand a chance to run smooth ! I cannot speak for other models but I hear similar complaints .
Never had any wobble / vibe issues at all on the RS Ross, to 100mph plus and steady as a rock all the way up and back again. If it wobbles or vibes there's definitely something wrong somewhere.
The problem with asking questions like the O.P has asked here, is that on forums / social media etc a proper diagnosis is impossible without actually seeing and driving the car - the problem could be one of a number of things, so any advice given without actually seeing it is purely based on conjecture at best - and certainly on Facebook groups downright bloody dangerous sometimes. Some of the "advice " I've seen offered there makes my stomach turn.
My advice to anyone asking questions like this is always the same: ....If you don't know how to check it out yourself then take it to someone qualified who can, brakes and suspension aren't things to be dicked about with, either of them can kill you or someone else when they fail.
Second all of that . My Mk1 Le was smooth as silk all the way to legal limit (I would say that) and back too . Bit rough on the ears mind you