Sometimes it's just best to separate the two. I ended up investing in a Thunderbolt dock, so whenever I want to get shit done I just plug in my MacBook and my Mac becomes a functional desktop system. When I want to play games, I just swap over to my Windows box. Not all Macs are super expensive, with the Mini and Air being fairly affordable options (mini-desktop and ultrabook, respectively), and the new Apple M1 CPU absolutely thrashes most of the Intel options on the market (while the GPU won't compare, the CPU in a $700 Mac Mini is likely to be quite a bit more powerful than what's in your gaming rig, crazily enough).
Audio in Windows is a complete disaster. One thing that I've found that can help is disabling playback devices that you don't intend to use so that it doesn't randomly bounce to something that won't output any audio. On top of that, routing is sort of hit or miss, with some applications refusing to go to a different source until you close and reopen them. The biggest issue I have is that sometimes Windows will refuse to list my VR headset in the audio options, forcing me to go into the old Windows 7 sound control panel just to get the system to realize that the audio device is there. It's absolute lunacy.
Generally speaking, you'll want to stick with the popular distros if you don't have much background knowledge going in, as those tend to be better supported and are easier to install. That generally translates to one of the Ubuntu variants. Ubuntu (with the GNOME desktop) and Kubuntu (with the KDE Plasma desktop) are the two you'll want to focus on, methinks. I find that KDE's interface is a bit easier to slide into when you're coming from Windows, so I'd recommend starting with Kubuntu. I should also point out that the choice of desktop environment does not impact the applications that will be available. If someone recommends a piece of software in Ubuntu, you can easily use it in Kubuntu without any issues. Similarly, if a developer provides a package for Ubuntu, that package will work equally well in its variants.
The Raspberry Pi 400 is a good platform for tinkering, but one potential issue is that the UI is pretty distinct in order to cater to the platform's paltry hardware acceleration. Most desktop distros use something like GNOME or Plasma, and while you can run those on the Pi they tend to be a bit too heavy for it. If you just want to learn Linux itself, however, it's a pretty solid choice, and since it's based on the same system that Ubuntu is based on (Debian) a lot of command line stuff will translate over.
As far as how to pick the distro, you basically have to know enough to understand your needs and look into the distro's feature set and other unique utilities (package managers, mostly). Having a spare box to experiment with helps. Generally speaking, each distro is catered to a specific need. Arch caters to people who want bleeding edge software, Gentoo caters to people who want the ultimate flexibility and don't mind having to compile the source, Red Hat Enterprise is catered toward businesses who don't mind paying for support, while Ubuntu is catered toward the average Joe (not to say that it isn't powerful, but it's not exactly specialized). Honestly, unless you're unsatisfied with a particular aspect of a given distro, there's no reason to move from it.