I am not aware of any issues with these countries but if you want a definitive answer you will need to read their AIPs.
Some of them may however require VFR flight (I presume this is a VFR question) on specific routes, so you cannot simply fly outside CAS like you can do everywhere else. Often, these routes are on the published airways. Greece likes that kind of thing, for example, and Montenegro and Albania also require specific routes and will refuse a VFR flight plan through their airspace if these are not followed.
So it's worth asking if specific routes need to be flown. I suspect it will be a minimal issue, but I would be suspicious of Macedonia.
Note that this is not the same thing as flying the "level level VFR" routes which are seen on some VFR charts e.g. Italy; these don't mean anything other than provide low level (generally below 1000ft) routes through CAS, and they tend to be used by local pilots.