Did a trip like this a few years ago. Highly recommended, if you have the opportunity!

Wanted to do a write-up like this, but only got as far as the map,

https://kenschutte.com/europe-2023/

I wonder if they took the new "Rail Baltica" through the Baltics? That was one of weaker links in the train route - I used a bus between Vilnius and Riga.