Hi Lulu, I love to plan & research, too, and even used to get paid to organize processes at work before I retired.
For many years, I had paper copies of our plane ticket, each hotel reservation, train tickets, activity reservations, Google map of route from train station to hotel, a set of papers for each city of ideas paper clipped with the section of the RS book for that city. The cover page was an Excel summary page of Day, Hotel & address, whether it was already paid, train departure & arrival, and the main activities planned for each day. Activities with reservations were color-coded in turquoise, hotels already paid were highlighted in green, and Sunday dates were highlighted in yellow (to avoid train travel).
Two years ago, I started using the TripIt app. The first year, I printed out the list from TripIt, so I could refer to it on the train without pulling out my phone. I still brought paper copies of everything listed above, except I didn’t need the papers of possible activities- those were loaded into TripIt into days I would be in that city with just a placeholder time. In other words, I would choose a subset of those activities but had the options in TripIt. I liked that I could insert a possible restaurant or gelato shop, and TripIt auto loads the address. The sections from the RS guidebook were only a couple of pages each. Since that trip was my first solo trip (celebrated by retirement with three weeks in Italy!), I also included an Excel summary page just of train travel: Date, city departure train station name, arrival name, departure & arrival time, reservation code, PLUS I added Plan B & C if I were to miss that train.
Last year was another solo trip for two weeks, and my husband joined me for the last week. I organized everything the same, except I didn’t bring the paper Google map, and I didn’t print out the TripIt details. I did take photos of maps, etc. and kept those in iCloud folders of each town. The biggest benefit over the past two years is that I don’t have all of the activity option papers to carry. But, I really missed the printed paper Google map. It was nice to orient myself to the town, and I always marked a few highlights on the map besides the train station & hotel. Reading that from a paper vs. a phone display had been much easier - I missed it and will add it back this year.
Two other things I do: if I book a reservation with Booking.com, I always use the option to print the reservation in the hotel’s language - just a courtesy to them vs. handing them a reservation written in English. And, if my husband is traveling with me, I always give him the same papers of the Excel summary & all printed reservations as a backup plan in case my suitcase was stolen.
Another helpful item to write on a paper - I usually purchase my train tickets on-line ahead of time, but I bought one at the French Riviera last year. Noticing the slow-moving line & interactions, I wrote “my destination city, one person, and requested departure time” in French on a Post-it note. Wow, my transaction was so much faster and appreciated by the desk clerk!