I think a lot of this is your aesthetic decision, but I would imagine that carpeting may be softer under foot and also help keep the noise down in the rooms and help with decrease sound traveling done to te floors below. Any humidity problems which h would create mold issues in the carpet?

You have vaulted areas between the floors that can and will create an echo chamber with hard surfaces in BOTH spaces. Right now the carpet is dealing with as much noise as possible. As soon as you remove the carpet you will notice echos traveling all over the place. And if your vault/space is BIG ENOUGH (yours might be...hint hint) you can get an irritating 'hum' or 'buzz' going on. This can be there even when there is NOTHING creating sound. We hear this in large stadiums, old libraries (with stone flooring), churches, etc.

The easiest way to figure out what the carpet is dealing with is to REMOVE the carpet and then 'live' with it for 2 weeks. Have people in the house moving around on the plywood subfloor. All the banging, stomping, echoing will be there with LVP and with tile (and possibly hardwood as well).

The space was designed for carpet. The carpet was used in the design to 'knock down' the noise and to prevent it from disturbing the 'up-down' living situation.

I would be very cautious about moving away from carpet in the mezzanine/hallway areas.

We did tile on the bottom, coordinating carpet on the stairs and LVP upstairs. It all coordinates and you can’t see any of the flooring from upstairs from downstairs or vice versa. I did not want tile upstairs because it’s not soft or comfortable, however LVP is, and it’s waterproof (senior dog who likes to leave surprises for me) and kid proof. It’s also not noisy. We had it glued down and used the highest end padding system. I think that makes a difference.