I reserved an Enterprise rental car for our 2+ weeks in Croatia and surrounding area in September, pick up in Rovinj, drop off in Dubrovnik. I received the best rate via Enterprise directly but they reserved it as "pay later". I always feel a bit anxious about not having a paid reservation; it seems more likely to have issues, but maybe I'm over-thinking. I assume I can call to pay for it, if needed. Thoughts?
We rent from Enterprise quite frequently, and always pay when we pick up the vehicle. Never had a problem.
You might look at Uni Rent (a Croatian company). We are renting a Renault Captur for 8 days, with GPS, WiFi (!), and maximum insurance coverage (that way no one "finds" some scratch and wants extra money), pick up in Dubrovnik and dropping in Opatija. Under 650 euros.
They do not have drop off or pick up in Rovinj. But we are going there as well (en route to Italy) and booked a private transfer for the two of us using Goopti, for about bit over 100 euro from Opatija to Rovinj.