I absolutely hate toothbrush style ear phones. which essentially limits my options to just Samsung or Google. I just change between these 2 every couple of years.
Tailscale is great, my 3VPSs and home server all are connected over tailscale, I can route traffic from internet to my home server without having public ip address at my home. Everything is running flawlessly from last 1 year,
My wife has S20FE 5g, still no complaints, but there won't be any further updates, so won't recommend it. Look into motorola, they have quite good phones in recent years.
I would also recommend getting a proper lab bnch power supply instead of using an ATX Power supply. You get much more features and it will be much more reliable that converted ATX power supply. I also won't trust my tinkering skills for something that has live AC power involved.