..., how did all those guys in the 80’s stay in tune, I guess that’s why they switched guitars so much on stage.
Because of the Floyd Rose Tremolo they used. When it comes to tuning stability there is nothing that beats a system where the strings are locked on the bridge AND the nut a.k.a. double-locking-system.
There is no secret behind the correct set-up of a double-locking tremolo-system - in fact that is probably one of the best documented things in guitar-diy on YT nowadays imo. And again - a correctly installed and set-up Floyd NEVER lets you down.
Btw: I can´t remember any more excessive guitar switching on-stage in the 1980s than there is today because of different guitars for different tunings mostly
Practice cures most tone issues.
Great Deals with MrWhipper, JoeyM, Del Hudson, skydive69 and Kramer Classic I