Slovenia, Croatia, Bosnia, Montenegro Roadtrip?

Me and my girlfriend (Canadians in our late 20s) are planning our next trip together and we have settled on doing a roadtrip in the Balkans. We want to fly in to Ljubljana, Slovenia, rent a car via Europcar, and explore cities, national parks, and beaches throughout Slovenia, Croatia, Bosnia, and Montenegro. We would make our route a circle so we can drop the car off in Ljubjana and fly home to save money. We have ballpark 18-20 days and will be doing it late summer 2026.

Now, I’ve never been to Europe and my girlfriend has only seen the Western European countries. I was wondering if I could get some advice and ask some questions to anyone with experience in the region.

• Is 18-20 days enough time to do all 4 countries or should we sacrifice Montenegro to see more of the other countries? I would realistically want to be driving every second or third day during the trip so 2-3 nights in each location.

• Will Europcar allow us to rent a car in Slovenia and travel to these other countries before returning it without a huge upcharge? I dont see anything about international coverage on their website.

• Should I expect any funny business or long waits at any of the border crossings? Will I just need my passport? As far as I’ve read, none of these countries require Visas for Canadians.

• What are the safety concerns in these 4 countries? From what I understand, Bosnia is the most sketchy but still fairly safe

• Will I be able to get by with just English in all 4 countries?

• What are some of the must see locations along the way? We like fine dining, nice hotels, seeing natural beauty, hiking, swimming, museums, historical sites. We don’t really do clubs or parties but we do like to drink.

If you read all this and have anything helpful to tell me… thanks!!