gksu and kdesu are unsupported for >10 years iirc, they were not more secure than sudo and that’s one of the reasons they were abandoned. I’ve never heard about sux. Polkit is a bit another thing that indeed replaced them, however it does not and can not separate GUI and non-GUI processes. The process itself has to fork, drop privileges and draw a GUI after that. There’s no difference between running it via sudo or pkexec, however polkit provide additional protections to prevent running unsafe apps with elevated privileges.

PAM and GVFS are not “privilege elevation frameworks” whatever you mean by this.