I just uploaded the photos from my trip to that area in July. We spent 6 nights based in Rovinj and visited Pula and Porec as well as several hill towns including Motovun and Groznjan. There is a town called Oprtalij which is just across the valley (and the main road) from Motovun. You can actually see it from Motovun (just barely) but it takes 20 minutes or more to drive due to winding narrow roads, but it was so worth it. Much less visited than the others, still partially in ruins, but we loved it. Check out the photos of it (and the other places as well) https://andiamo.zenfolio.com/f244307974
As I said, I'm just now getting the photos posted so they aren't all labeled yet, but the "Istrian Hill towns" gallery has the town names labeled.
We arrived at Plitvice at 3:30 and toured the park for a few hours, stayed the night (Hotel Bellevue) and went back in the following morning. Can't remember the names of the road we took between Rovinj and Plitvice but it was pretty much whatever google maps said. It took longer than expected.