Bikepacking Yugoslavia

I’m going to navigate the Balkans in June. I’ll have roughly 30 days and will be using hotels. I’ve booked most already through booking.com

I wanted to ask:

Is it cheaper and easier to just book places once I get there?

I will be using a cardboard box and trashing it at the airport and riding straight from there. What are my options for a second pair of footwear that is packable (for airplane and the few days of rest I have?) I’d like to keep my bike weight under 15kg with water.

Any tips for the route?

What are some must do things in each of the places I stop at?

I’ve also added my pack photo. What is something I am missing or don’t need?

Shoe covers
Shorts
Thin pants
3 pairs of socks
3 bibs
Buff
Cycling glasses
Sun cream
Lip balm
Rear light,
5000lm front light w/20000mah battery
1000ah battery
Assorted cables
USB c charging brick
First aid
Emergency blanket
Arm warmers
Cycling cap
2 short jerseys
Thin gloves
Thick gloves
Toiletries
Ibprophen
Anti-diarrhea tablets
Hooded rain jacket
Warm cycling jacket
Cycling warm base layer

Any advice would be greatly appreciated.

Here is my planned route, each section is a day:

https://ridewithgps.com/collections/3964999?privacy_code=Z9NGKqKVjubOYxxQ4EIckvK2BRozypA6