Alex,
I’d recommend that you first get clear on what you expect to get from a 4K camera. From your post it’s not clear to me why a 4K camera would be right for this project.
Don’t get me wrong. I have a Panasonic GH4 and I love it. I almost always shoot in 4K, mostly for the ability to crop in post. For the type of work I do that’s a huge advantage.
But be clear on your expectations and don’t forget that editing 4K footage requires a fairly capable PC.
Dave
https://photoperformance.photos/