I solo'ed around Germany earlier in the

[tulip fiber]

planning on soloing through a few parts of italy and also amsterdam & rotterdam, I have zero experience with public transport and don't know how complicated moving through these countries is, I also started the trip at a friend house so I came with luggage but maybe it's better to keep part of my luggage there and buy a travel backpack for soloing? since moving a suitcase through a new city every 3 days doesn't sound that fun

and for social activities and meeting people what was your go to thing? staying at an airbnb can take a lot of opportunities for that

[silver nimbus]

For the most part you'll be getting through everywhere with trains. You may need to catch the occasional bus but trains are way easier and aren't as subject to timetable fluctuations

moving through each country really depends on how far your accomodation is from the train stations

how are you getting from italy to amsterdam? plane?

And how large is your luggage

Travel backpack may be a good idea if its very big, but something that you could do is put in lockers that are located at the main train stations usually. And if you ever need to get something from it you just go to that train station