After Apple's recent upgrade to iMovie, I noticed the uber-fluidity of iMovie's cursor-timeline interaction—it's amazing. So "natural-feeling," and you don't need to keep the mouse-button depressed to scrub the timeline—a refreshing feature which makes browsing the timeline a pleasure. I've been fooling around with iMovie on my late-2015 27" Core i7 iMac and I'm now considering Apple Final Cut Pro instead of upgrading to Vegas Pro. But apparently some FCP users are experiencing major issues on Big Sur (the current macOS).
There seems just as many complaints about FCP's stability on Apple's forums as there are about Vegas' stability on Magix' forums (Vegas actually runs great on my machines). Of course the many happy users typically have nothing to post about so we never hear from them (which may be the vast majority of users). If nothing else, Apple's UI-design sets a very high bar, superior to that of Windows/Vegas.
Even on a six-year-old iMac, iMovie runs like a champ using 1080p24 media files—no fancy Ryzen CPU or dedicated, $1,000+ GPU required.