I'm quite a large fan of Debian, it's my go to choice for anything server personally. It's pretty good for what you want here IMHO, it's stable so you won't really have to worry about packages screwing you over and like another comment said you can stick unattended-upgrades on it :)
These are VPSs. You can SSH, use the root user, and when setting up you can choose what OS to use, they give a list or iirc they let you upload your own ISO.
Yeah, I don't do anything fancy with mine, I used to use quite a few VSTs on my other mics to get the sound I want but honestly... the SM7B at its default settings, no low-cut, no other EQs, no compression, etc... it just sounds right on my voice
I recently just got my self an SM7B. I love the thing. I don't do WFH so my work mates won't ever get to hear my wonderful voice on it but oh well, eventually they will! I love it. You do need a beefy interface to power it, I have an Elgato Wave XLR.