Hey! Sounds a great trip - here's my tips.
Paris - I wrote this article and can personally recommend pretty much everything on here. Chez Omar is cheap and the food is fantastic, same for Chez Aline at lunch. The Saint Chapelle was a real stunner too. https://www.secretescapes.com/magazine-uk/paris-beneath-the-tourist-trail/
Switzerland - Switzerland is just pricey. Beautiful, but jeez. Maybe stock up at a supermarket for snacks, lunches etc to save a few francs.
Tuscany - Ive not been to where you're staying but it looks fantastic. Tuscany is famed for dishes like fagioli (great for lunch) and a very specific steak, minimum kilo order, best shared. dont miss that its gorgeous. Always just go for house wine by the glass, brilliantly cheap and always great. If youre going for dinner or lunch, you dont need to get 3 course, you can just order a primi (pasta dish). The menus sometimes make you think you need a primi and secondi, but its a personal choice not a prerequisite. plus portions are always huge. Dont miss apertivo at a bar before or instead of dinner.
Rome - The forum is the best thing ever if you love history. the ticket gains you entry to the Coliseum next door too. by the ticket at the forum (no queue) rather than the coliseum (hours of queuing. madness!) Rome is very walkable, dont bother with any transport. buy one water bottle and then fill it up at the many public water taps around the city. Trastevere is a great area for a drink in the evening, quite youthful and full of cool bars.
Venice - Best tip for Venice? Just get lost. It's stupendously beautiful, and getting lost is the best way to explore. Chicetti is the veneto version of aperitivo. its okay. There is a fantastic wine bar right next to the Rialto bridge thats dirt cheap and the wine is fantastic. Al Merca. Stay off the tourist trails. get lost. did i say that already? Also recommend the jewish quarter for something a bit different.
Munich - Do not miss the Asamkirche. one of the most beautiful rococco churches ive ever seen, and totally hidden away. Other than that im not as imrpressed by munich - the beer halls and food is great though; Donisl is great if youre in the centre of town, and i also liked the augustiner halle too. If you have time, getting a car and driving down to Neuschwanstein is a must. If oyu ahve more time, add in a trip to zugspitze; its a costly ticket, but totally worth it. Nothing quite like having a weissbier on top of a mountain.
Boppard - Not been. Looks nice! The whole valley was part of the grand tour, very popular with the Romantics. I would personally hire bicycles and beer garden hop along the river.
Amsterdam - Plenty covered above, some great record shops for sure. the main flea market is also decent, theres lots of island records in amsterdam; bajan stuff for example. Dont miss some of the old brown cafes (dutch version of a pub). my fav was cafe chris, its a time capsule spot - ask the owner about it. Amsterdam is bigger than you think, spend days walking the canal ring (or cycling). if youre into architecture, het Shijp is worth a trip. Other than that, get some hash, get some beer and just chill. its a beautiful place.
Greenwich - There is just too much to do in london. From north greenwich you can get the thames clipper into the centre of london. its a boat thats part of public transport. best way to travel. if you have a contactless debit or credit card you can just tap in and out of all transport. if not, get an oyster card and you can load money onto it for travel. Greenwich has 2 record shops, pretty place. get lunch at the market. Best pub there has to be the cutty sark.
If you need nowt else then shoot me a message.
have a great time!