I own a Linnmon/Adils table, which I have been using for a few years now. Still is a great table, but it has bowed in the middle a few cms, which is very noticable. Still supports all of the weight though.
You should look at a better case, Cooler master has good ones, and I have a soft spot for Lian Li. On the topic of an AMD build, I think you could go for a R5 5600x with a cheap B550 motherboard.
Yeah, totally go for a b450 instead and get a better gpu. Nvidia has been having a bit of driver issues with dpc latency and random short freezes, but I prefer their implementation of Raytracing and also dlss.
You might want to look into Nixos or Nobara Project, they provide options outside of GNOME, and have a lot of cool features. Was contemplating daily driving Nobara myself.