How are you going about importing from your GoPro? I have a Hero that's a couple years old and I've always first copied the files from the SD card in the Finder and then opened iMovie to import and that method works with iMovie 10.
The camcorder I have is a seven year old Sony DCR TRV-22. It's a SD NTSC camera that records to miniDV tape. I don't use it much anymore but it does work with iMovie 10 although I have to crop the images to pillar box them in the 16:9 picture format that iMovie 10 is limited to.
The only other camera I have is my iPhone 5S which works just fine with iMovie 10.
Unfortunately, I don't have any first hand experience with any newer camcorders such as you are looking for. But if I were buying one today, I'd probably look for another Sony that records on an SD cards.
Matt