Yeah, I don’t have first-hand experience with Arch for that reason either. Well, and also because I do want a distro to set things up for me. You could set up the snapshotting (with BTRFS and Snapper) on theoretically any distro, but not having to figure out how and what settings are good, that’s why I go with openSUSE.
I might look into NixOS at some point. It obsoletes the need for OS snapshots, because the entire OS configuration is made in configuration files. But from what I hear, it helps to be a programmer (which I am) to really appreciate NixOS.

And yeah, don’t know much about Bazzite either, but from what I’ve heard, it really has some design decisions that make it feel more like a games console. The atomic/transactional updates, for example. As I understand, updates and such are applied to a copy of your OS, which gets swapped in when you do the next reboot. This helps keep the system stable after applying updates, but implies that you can’t really just poke around manually in your root partition.
It can be helpful for users not looking to experiment, but yeah, can be a pain, if you do want to.

As for a real-time kernel, the JACK FAQ says you don’t need it, but the distro might limit real-time scheduling anyways: jackaudio.org/faq/linux_rt_config.html
I’ve had JACK running on my system about a year ago, although I didn’t really have a need for low latency, so I can’t say, if it actually worked correctly.
Perhaps also worth pointing out that “Pipewire” is becoming a thing, which tries to make interfacing with JACK and PulseAudio much easier. I believe, I also used Pipewire back then. But yeah, folks who’ve dealt with JACK a lot more than I have, seem to be really excited about it, so it’s presumably doing a great job.