Montenegro probably resembles what Croatia was like years before tourism got ahold of it. The country is filled with sleepy coastal villages, insane backdrops in every direction you turn, and wonderful beaches sans crowd. I wouldn't go as far as saying this is the 'it' destination of the Balkans, however, it's definitely a cool place to road trip through especially given the small size. I'd recommend Montenegro for the older crowd or couples, as that majority of people we saw were 40+ and/or couples. There are a heap of opportunities for outdoor actives such as hiking, boating, and swimming, so if you're into the untouched outdoors, add Montenegro to the list! I'm sure it'd also be a gorgeous place to sail along the coast, but we didn't have that luxury ($ help us, we're poor $). Our road trip did bring us all over the country, making stops in Kotor, Budva, Sveti Stefan and Ulcinj.
Kotor was the most picturesque, with a stunning marina and a crazy castle hike where you'll see the best views of your life. We found out as we drove on that each place has an old city and most of them are protected by walls which is really cool!
Unfortunately, the traffic and road system of Budva really threw us off, so we bailed and went straight to Sveti Stefan. The surrounding area here is great for hiking and the beach itself is really unique. I wanted to get as close to the Albanian border as possible, where we found Ulcinj! I'd definitely recommend checking out this sleepy beach town if you have the chance.
Overall, if you're a solo traveller or single for that matter, I think Montenegro would be best saved for when you're in a relationship, married or retired.