"video for the sizing die it says screw die down till it touches shell holder then, lower shell holder and screw the die in another 1/4 turn isn't that considered over camming?"
Trying to 'adjust' dies by rote only gets us in the right ball park, it sure won't work any magic in set-up. No straight wall case needs to be jammed as far into a sizer as it can go anyway. You may easily leave a 1/16" - 1/8" gap between the shell holder and die for straight wall handgun cartridges.
"Cam -over" is a function of the lever/toggle block cam effect. It occurs when the toggle block rotates passed top-dead-center and the ram has started back down. Meaning cam-over happens when the lever is fully depressed whether a case or die is in there or not.
Turning a die 1/8 th of a turn moves it some 9 thousanths of an inch; by itself that's a massive change. In fact it's about half again the full min to max headspace range of most bottle neck cartridges. But the amount of stress change needed to accomplish what needs to be done varies according to each individual press, its linkage and the die/shell holder tolerances. Meaning even a more critical rifle FL sizer adjustment has to be done for the proper effect, it's never a preset adustment forever and ever, amen.