In reply to PPP:
A friend and I did all of it except the last bit of Kosovo. We did run into some unmarked sections in Kosovo and life would have been a lot easier with a GPS!
We didn’t book accommodation in advance. In all the little settlements/villages, people would offer to let you stay in their home, and there were occasional hostels. Important note is if you stay in someone’s home, always offer money (about 20 euros is fair) but only offer the money to the family’s children, don’t offer it to the adults.
The terrain is varied. Some easy forest bits like the Loch Lomond bit of the WHW, other bits quite steep, like going in and out of Okol. We took 4 days and would have needed a fifth to finish.
Get food when you see it!! It was hard to come by anything more substantial than bread, veg, and fresh cheese.
Learning a little Albanian before you go is a good plan and really improved the quality of the trip.
Btw there are quality boulders on the top of the pass between Okol and Valbone if you want to pack rock shoes...