mostar

You could actually do it in 1 night, but 2 is maybe better so you have a full day in Mostar. I would do the sight seeing on the way to, and from Mostar so you dont loose so much time trying to park the car every day.

You could stop at Blagaj Tekija on the way up and Kravica on the way back(or the reverse), then there are a few small towns along the way. The two I stopped at were facinating and beautiful and very different from each other. One hillside, one river. But I dont know your route. I had the advantage of a local that knew where to go, where to eat, what to see. Costs, hours, etc. (paid transfer). At Kravica the boat sounds interesting. I just went swimming.

So you are looking for flat? Flat and Mostar are two words that dont coexist.

Mostar is pretty small, 2 nights would be about right. The day trips to Kravica and Blagaj won’t take a ton of time either, so you’ll have time to explore and enjoy Mostar in the morning/evenings. Depending on where you’re driving to/from they’re almost roadside stops.

FYI, if by “boat tour” you mean the ones at Kravica, they’re small row boats that go right up to the falls. But the falls are basically a big (gorgeous) bowl, and the boat takes you a few feet outside the swimming area. It’s not like a big excursion, just a few pleasant minutes. Kravica was pretty fun, waterpark amenities with natural beauty, but Plitvice it is not.

One night was way too short for me. If you are doing a day trip from there, I would do 3 nights.