I haven't seen these yet although they've both long been on my "to watch" list since they came out. I love CITIZEN KANE, THE MAGNIFICENT AMBERSONS, OTHELLO, TOUCH OF EVIL, and CHIMES AT MIDNIGHT, but haven't mustered enough interest in late Welles to get to these. F FOR FAKE left me bored.
After finally watching and enjoying Citizen Kane, I watched MacBeth and recently enjoyed Welles in The Third Man. I've also watched a lot of interviews and tv appearances with Welles on YouTube.
The ones you mention are on my list. Weren't Touch of Evil and Ambersons both critically acclaimed but Welles said they had been hacked up by the studio? Aren't there recuts for both films? I hear Chimes at Midnight may have been Welles' last great work.
F for Fake looked like an interesting experiment, kind of like Other Side of the Wind. What was bad about it? Just boring?