I did Bulgaria and now thinking Bosnia Serbia and mmmaayybbeee if you think it’s worth it Montenegro (but I do feel content without it). Those two good pairings? I dont have a timeline on how long either so pretty open. Thinking a late summer or early spring trip. I like interesting history (Bulgaria Roman ruins, communist era, etc) and appreciate how even tourist areas in the country still felt lived in not got the whole tourist polish and culture felt preserved vs just an instagramable moment.