Each panel is a separate app, same as before. But in the old version there was animation that hid the delay.
VLC doesn't launch a new process each time it changes panel.
Yeah, System Settings is even worse on an Intel i7 16" MBP with AMD 5300M GPU enabled.Then Apple needs to add some sort of transition animation back, because this feels broken. Regardless of what may or may not being going on "under the hood", users aren't expecting a lag like this when clicking a paned menu, so there should be some sort of transition at the very least.