Please rate my 18-day Croatia/Bosnia/Serbia itinerary

I'm traveling solo, using public transport. I tend to fit in quite a lot more that other travelers - I travel fast! I don't really like to "chill and people watch"! I have to make it to Budapest on Day 18 - I'm meeting my sister and we're renting a car for the rest of the journey (Hungary & Romania). I do enjoy wandering around old cities and beautiful natural scenery; not that much into museums.

Day 0 - Land in Zagreb 19:40ish (Night: Zagreb)

Day 1 - Zagreb (Night: Zagreb)

Day 2 - Zagreb - Possible day trip to Ljublana and Lake Bled (Night: Zagreb)

Day 3 - Bus to Plitvice NP (Night: Plitvice NP)

Day 4 - Explore Plitvice NP, afternoon bus to Split (Night: Split)

Day 5 - Split (Night: Split)

Day 6 - Split + surrounds (Night: Split)

Day 7 - Split + surrounds (Night: Split)

Day 8 - Bus to Mostar (07:30-12:10) (Night: Mostar)

Day 9 - Possible halfday trip to Kravica Falls, then 17:09 train to Sarajevo (Night: Sarajevo)

Day 10 - Explore Sarajevo (Night: Sarajevo)

Day 11 - Day trip from Sarajevo (Night: Sarajevo)

Day 12 - Bus to Podgorica – as far as I can tell, this only runs every other day so I can’t move this by one day (Night: Podgorica)

Day 13 - Podgorica to Belgrade scenic train (10am-21:30) (Night: Belgrade)

Day 14 - Explore Belgrade (Night: Belgrade)

Day 15 - Explore Belgrade + train to Novi Sad (Night: Belgrade)

Day 16 - Day trip - Eastern Serbia (Night: Belgrade)

Day 17 - Day trip - Danube fortresses (Night: Belgrade)

Day 18 - Train Belgrade to Budapest