There is nothing worse than visiting a country and falling in love with the place, then wishing you had allowed for more time. I also acknowledge that even the smallest of countries can take years to explore. However..... I only have 10 days!
Would Estonia, Latvia and Lithuania be achievable in this amount of time using public transport?
It really depends on what you're looking to do. It takes around 4 hours to get from one country to the next, which isn't so bad - I recommend using Ecolines as they're cheap and comfortable. The cities in these countries aren't very big so won't exactly take you a week to walk around each one.
Tallinn, Riga and Vilnius have to be on that list and you can maybe add day trips to places like Trakai, Hill of Crosses, Jurmala or Lahemaa National Park. It's possible to do them in 10 days but I'd recommend more time as the countries really are beautiful. I really enjoyed the capitals the most but these countries won't be going anywhere soon so you could always go back later and do them more in depth, maybe?
Thanks for the advice. I have used ecolines before in the past and they are indeed very cheap! I've researched your suggestions and I think I'm going to go for it. All 3 countries just look fantastic!