>as I've seen on reddit some people saying it's pretty jarring when it switches between 48/24 FPS

I think it was jarring, and the switching of fps was distracting when I saw it.

I would go with the 24fps if I had to pick one. Avatar is "epic" enough for motion blur to work well.

For context, I own Gemini Man, Billy Lynn's Halftime walk, and I saw saw Hobbit in HFR....

Where TrueCut Motion comes into play are like long panning shots of a landscape, where the pan speed doesn't sync with the camera's fps, and you get judder. I am all for fixing that in post.