

Does it have to be a new laptop? What you’re describing is basically a used work laptop. I’ve gotten to take my work PCs with me upon leaving, and I use them still. My current work laptop is in fact the work laptop from my previous employer, only with a fresh reinstall (Linux Minr Debian Edition), and it works well.
If you’re able to source a 2nd hand Dell, you’ll probably have what you need. Might need a battery replacement, but that’s easy enough to sort out.
Linux Mint works pretty well out of the box for most installs, so I suggest you give it a try and see if it does what you need.
Yes. Newest version of mint uses pipewire as audio engine, and if you combine that with the good old pulsaudio controller (which works with pipewire via a plugin), you can micro which app input/output goes to which device.
This works more or less out of the box. I think I remember needing to install pulseaudio-pipe or something similarly named, or it might be included by default.
Source: When working with audio I have multiple audio hardware running at once, each with different behavior and associated software.