If the Uffizi, etc. is sold out of advance tickets from let's say 8:15 to 11am, do they still admit people from the ticket line before 11am, or should I not show up until 11am. Let say I get to the box office at 8:00am and there are just a few people in line...would I have to wait until 11am to get in.....just curious about this...Thanks!!
Get the Firenze Card. You won't need reservations.
Both reserved and non-reserved lines start at the same time, so theoretically you could show up early but expect more than a few people in line, even at 8am in summer.
The Firenze Card is a little pricey if you only want to visit a couple of sights. You might try a ticket broker, you'll pay a bit more than a regular ticket but they may still have some for your preferred time.