Just got back from Italy and Paris. I like the second itinerary. People told me to cut Cinque Terre from ours because we only had two nights, but it was magical and I'm glad we stayed. There's not a lot to do except hike and eat so we could have gotten bored (or not, who knows?) but with 2 nights, it would only be worth it, in my opinion, if you stay in Vernazza proper or one of the other 4 terre. La Spezia is cute, but sleeping by the ocean in one of the most beautiful villages in the world is a real pinch-yourself moment.
I feel that Florence, in particular, is not great for short visits even though the center is very walkable. There is immediate beauty, but I feel it takes a moment to find the soul and I wouldn't want to try in 2 or 3 days.
I'd only stay in Pisa overnight if I wasn't going to try to "do" Pisa, but just get my sea legs and snap a few tower photos and get a gelato on my way through. (We flew from Pisa to Paris ourselves.)
Rome got my heart and I feel like I could live there. We took a tour we loved in Rome- very out of the ordinary and so much fun. It was our favorite thing we did in the city and it's a pay-what-you-want thing-- and in the evening when it's harder to find things to do since the big sites are closed. ( https://www.guruwalk.com/walks/38348-free-walking-tour-of-ghosts-and-mysteries-of-rome ) We were there for 4.5 days and we were able to do a ton in that time, but I probably should have taken it a little slower for our enjoyment.
We loved staying in the Pantheon area and transportation was easy from there, but we could walk pretty much anywhere. If you have any very specific questions about logistics that I could possibly answer since my memory is fresh, don't hesitate to message.
We only stayed in Paris 2 days and I'm mixed on whether I wish we canceled it and stayed in Italy. I think we probably would have had a more enjoyable trip over all, but it's hard to wish you never saw Paris even though we had a tough go of it there. I think our short stay may have had something to do with our inability to connect, though Paris seems to be a very love/hate thing for people. If you let me go back to Paris or pretty much anywhere in Italy tomorrow, I wouldn't even blink choosing Italy. If you do go to Paris, we enjoyed 59 Rivoli a great deal and I know it doesn't make he cut for many visitors.