OK, knowing that it's queues you want to avoid helps.
There are usually ways to do that, and the choice depends on the type of traveler you are? My husband and I almost never do tours: we pre-order tickets/buy passes, and use books and online research for our sightseeing. We are dawdlers who like to explore on our own schedule and don't like to be moved along until ready to do so. I knew I couldn't do a 2-hour tour of the Uffizi (needed at least 5 there) or the Louvre (3 visits) or Westminster Abbey or Pompeii (spent 5 hours at both of those and that was the 2nd time) or any number of other must -sees. I've spent hours in churches which maybe got just a couple of lines in guidebooks!
But everyone has different interests and comfort levels. There's no real right or wrong; it's all about what makes YOUR experience enjoyable. Not a reader? Then an audio or guided tour may be right for you. Have a passion and background in history or art? You may do just fine with a book in hand. Just don't book a tour simply to skip a line.