I'm a big fan of the mountain ranges for some hiking/mountain biking, and loads of different trails close to the house. (I have form on this, as I was a ski instructor, and lived in Andorra and the Chilean Andes.) There are several lovely ranges (Rila, Pirin, Rhodopes, Balkan) here, so there are plenty of options. There is some spectacular scenery around.
For example, Bansko (Pirin) is a very quaint little town, and Bulgaria's top ski resort. There are loads of great trails here. I enjoy it, but it just a bit too touristy (= more expensive) and a bit too far from a big town for my taste. But there are many who have it as a year round home.
I like the Balkan Mountains too, with the Central Balkan National Park which is not far from my house. The range goes across all of Bulgaria (but much lower at the coast), so there are lots of towns/cities/villages close by. So Troyan, Karlovo, Kalofer are not far from me. Veliko Tarnovo is on the north side, and it's lovely too (although not close enough to mountains for my taste).
I am in a small village near Shipka, which is a delight, I often sing its praises here. As I bought it sight-unseen (I was motivated mostly by how many trails showed up on google maps, and what the view of the mountains was like), I feel pretty lucky. Unlike many depopulating villages in Bulgaria, mine is a little boom town (boom village?) with all the old houses getting renovated, several fancy new mansions getting built, one of the residents digging a trench from Enina to bring fiber optic cable, and the mayor digging up all the streets to put in sewer lines. I just spent 2 years of Covid lockdown there, and it was kinda awesome... I didn't miss even one day of walking (testament to Bulgarian weather).
But there are several very nice villages in this area (known as Valley of the Roses, or Valley of the Thracian Kings). But Kazanlak is only 10 minutes drive, and maybe 40 minutes to Stara Zagora. So civilization is close by.
And it doesn't have to be mountains. There are other national parks. And the Black Sea coast with beach villages and inland villages. And down near the Greece and Turkey borders. So many places that you could choose!