travel from Sophia to Budapest via Transylvania

I don't have hotel suggestions because I can't remember specifics, but I can tell you that I have stayed in both Brasov and Sighisoara with no reservations in summer and had no problem with hotels. I landed in Bucharest and picked up a car, drove to Constanta and then up the coast and cut over towards the west and Transylvania. It is beautiful and I loved Romania. It was really an easy country to navigate, although driving was a bit slow as not lots of major freeways on my route. I left my rental car in Timasoara and then took the train into Budapest. It worked out great. Have a great trip. Everything was also quite reasonably priced.

Here's a suggestion: Day 1: Bucharest Day 2: Train towards Brasov with stopover in Sinaia to see Peles palace (1/2 day), Brasov in the afternoon; Day 3-4: Brasov, with day trips to sites on the outskirts (Rasnov fortress, Prejmer and/or Harman churches, "Dracula's" castle in Bran etc.); Day 5: Morning train to Sibiu, visit Sibiu; Day 6: Day trip around Sibiu (either to the villages in the Marginimea Sibiului area or to the monasteries on the Olt valley), evening train to Sighisoara;
Day 7: visit Sighisoara, night train to Budapest; As general advices on accommodations preferably use guesthouses ("pensiune") rather than hotels and choose places located close to the main tourist sites (specifically in Brasov around Sfatului square, respectively in Sighisoara inside the citadel).

Remembered our guesthouse in Bran, it was a great little place called Pensiune Ana... I took a picture of it, that's how I remember. It was across the street from an outdoor market, and also right near Bran Castle as well as a little grocery store, I think called Dracula's Market!