I traveled from Belgium to Lithuania in the last 2 summers, and also visited Riga, so here's some info that you might find useful.
I have a Model X100D and travel with a family. In the first day we do ~1200 km from Brussels to Kolo (PL) via superchargers (Kamen, Lauenau, Berlin, Poznan). There's a nice hotel Mazurek in Kolo with 3 Tesla DeCs.
Afterwards, it get's a bit trickier. You'll pass Warsaw, which has a brand new supercharger, but it is deep in the city, underground parking level -5, tight entry/exit, only 2 stalls. I used stop at Lidl (50 kw fast charger) or Galeria Polnocna (16 kW DeCs - good if you have more time/ wanna do some shopping ) which are close to the S8 road which goes to Bialystok.
Warsaw - Minsk: I never did this, so can't tell you much. You can go via Bialystok or Brest. On the PL side you'll have to use GreenWay Polska fast chargers - you can download their app and start charging sessions with it, but beware of the price (~0.5 EUR/kWh). Belarus also has many fast chargers, they are state-owned and free, but I don't have experience there.
Lithuania: the fast chargers are on the main roads and some cities, just plug and charge, for free. Vilnius is an exception: there is a big fast charger network there run by IgnitisOn which is not free (0.25 EUR/kWh) and you'll need their app to start sessions.
Latvia: extensive network on the main roads. To use them, you'll need e-mobi app, charging costs 0.15 EUR/min (i.e. 0.20 EUR/kWh if the power is 45 kW). I only charged once in Latvia, at the Akropole shopping center in Riga, where they have 6 free Type 2 chargers.
Estonia: was the first to build the fast charging network in the Baltics. Its particularity is that only Chademo and Type 2 plugs available, but no CCS. You pay 1.5 EUR per 10 min via ELMO app. I have never been in Estonia with my Tesla, so don't know more.
In all these countries best to have Plugshare app as it is mostly used there.
Hope this helps
