Yeah you can binge on museums with the Paris Visit museum pass. You have to try to hit as many museums as possible in a set number of consecutive days. But the line skipping is worth it. It's especially important at popular venues like the Louvre, Musee d'Orsay, Orangerie, etc.
Some passes come with combo metro tickets but those tend to be more expensive. Might be better to get a separate metro pass or a carnet of 10 tickets at a lower price. Metro system is great as all businesses list their location in relation to the nearest metro station.
However, you can see more by walking and taking buses, which use the same tickets and passes. Only tricky thing about buses is that it's harder to tell where they go. So nowadays, you can get an app which will use your location and you enter the destination and it will show you options to get there, including on buses. But you need data for your phone.
I binged on museums the first couple of times I went to Paris and other European cities. Even sat down to read the little placards explaining some of the works, artists and so forth. But now, if I go to museums, it's more to appreciate the architecture. They've poured millions into restoring these places and many have historic import like the Louvre being a palace of several hundred years old.
First time I went, in the '90s, there were few galleries which were air conditioned. On hot summer days, they opened the windows which overlooked the Seine. This was before the IM Pei pyramid. Now you have the beautiful courts with the statues and then the whole square with the pyramid heading out to the Tuileries. There's a cafe with a balcony that overlooks the pyramid and the stately buildings.
Orsay used to be my favorite, for the openness and the renovation they did. The Rodin museum and Invalides are also worth seeing. In fact, if getting a museum pass, it's a good idea to first go to a museum which isn't as crowded to buy the pass so that you can use the line skipping in more crowded venues. Invalides is a good place to get the pass, or at least, it used to be. It stores the remains of Napoleon and the gold dome shows the splendor of Parisian architecture.
As for parks, Jardin de Luxembourg is great in the summer. Of course Champ de Mars with view of the Eiffel Tower is great too.
In Rome, most of the places mentioned are great. The squares or piazzas are also big draws. Spanish Steps and the Piazza d'Espagna is a nice area. For day trips, Villa d'Este is nice.
