I took this tour as a solo traveler in June of this year. It was amazing! I found that there was a good mix of planned group activities and free time, which is important to me as I travel solo almost exclusively and value my time on my own. The other tour members were really great about including me if I wanted to join them as well.
The hotels were mostly great, except the one in Mostar. That one was fine, but had zero character and my room had a leaky tub. That was only for one night though, so not a big deal.
I can't speak to getting from the airport in Ljubljana as I came by train. I took an Uber to the airport in Dubrovnik at the end of the tour and it was super easy. I shared with one of the other tour members who was leaving around the same time.
I had a free day in Ljubljana prior to the tour and I used the time to wander the city and visit the castle and the Ethnographic museum. Both were enjoyable experiences. You could also visit some of the nearby caves. Other tour members did this and reported back great things.
I learned only basic phrases in the local languages prior to the tour and found it sufficient. I never encountered any language issues.
The tour is definitely not museum heavy, which was one of my reasons for choosing it. I am usually a great lover of museums, but was looking for a different pace for this particular trip and this tour fit the bill perfectly. I am dreaming of the time I can return to Split as I fell in love with the city very quickly. If you choose to take this tour you certainly would not regret it.
Feel free to PM me if you would like more details.