22 days! I'm so jealous. Our Italy trips are ten days. In your second itinerary, I think you have too many nights in Venice. I would do only two nights. Also, Assisi can be thoroughly enjoyed with one night which is what we did in 2008. We arrived mid-morning by train from Rome. Spent the entire day wandering through its beautiful medieval streets and charming shops, spent several hours in the Basilica San Francesco, and went to a free evening concert. Spend the night and left early the next morning for Florence. So this gives you back three nights for to do other locations (like another Tuscan hilltown) or to extend your time in others. I agree, too, with the previus poster who suggested you consider the type of traveler you are. We like to allow plenty of time for sopping up the Italian experience in a relaxed manner. We plan our days so we can stop for a cappucino or wander aimlessly or do a short afternoon nap to rejuvinate. And what do you enjoy - musuems, art, ancient history, outdoor spaces, churches, foodie stuff? This will help you figure out how much time is certain places. For example, I am absolutely fascinated with Renaissance art and history. So I would spend more nights in Florence. If hiking and outdoor experiences were my thing, I'd go to Cinque Terra.
Remember, planning, researching, reading, mapping - it's all part of the fun of a trip likes this!