not much use for the 100GB+ AI boards or server RAM for consumers. Tho homelab guys will be thrilled.
Enterprise wise, the used servers kinda always have been cheap (at least compared to MSRP or even after discount price), just because there is enough companies that want a feel good of having a warranty on equipment and yeet it after 5 years.
Nowadays old-gen server hardware can be a viable alternative to a new HEDT or workstation, which would typically use top-of-the-line consumer parts. The price and performance are both broadly comparable.
No. Up to you to cool. I use an Epyc based system as a home server and you can’t hear it. At a previous employer we built a cluster out of these and just water cooled them. Very easy.
This is a chassis and fan problem not a CPU problem. Some devices do need their own cooling if your case is not a rack mount. E.g. if you have a mellanox chip those run hot unless you cool them specifically. In rackmount use case that happens anyway.