I've flown Condor numerous times. We didn't have any problems. We don't check luggage. The food was fine in all three classes - Coach, Prem Econ and Business. Coach is tight with them (and everyone else, I feel) and I would not fly coach. Premium Economy was comfortable enough. The one time I flew business class with Condor, I was so happy I could have cried.
Condor will sell you a single ticket into Slovenia and out of Croatia - they often sell you the shorter legs on Lufthansa flights. We arrived late once into Frankfurt by a couple of hours and went right to a Lufthansa counter with our Condor tickets and got on the next flight.
I'm not looking for a hotel experience when I fly. I want a safe flight and enough leg room so that I'm not losing my mind as I sit there for 10 hours. Condor Premium Econ will work just fine for that.