Hi!
All mention places are interesting and worth a visit! I would add also Koprivshtica (small picturesque town with nice architecture). Spend 2-3 days in V. Turnovo (you may visit Dryanovo Monastery and the cave nearby, Etara - ethnografic complex, Sokolski Monastery, Arabanasi). Definitely there are tour agencies in V. Turnovo where you could arrange the transport!
For the rest of your journey I woud advise you to stay in Sofia and make day trips to Rila Monastery, Plovdiv and Koprivshtica or if you have sufficient time you may spend 1-2 nights in the mention places. The infrastructure is good and there is reliable public transport from Sofia.
Other beautiful places are Rhodope mountain, Ruse, the sea side but they are not that close to Sofia...
Habe a great time in Bulgaria