Building a PC vs Server

[KingMongkut]

Hello!

I have built a few PCs in my life and I was just wondering what the difference is between that and a server (for plex, minecraft, general backup...)? Water vs air cooling? Do I need to go with a server cpu (like Epyc or Xeon) or can I just use a regular one (ryzen or intel i)? How much RAM should I get? Should I use Windows, Ubuntu, Pop OS, or something else? Does hyperthreading help? How many cores should the CPU have? Will a gpu have any noticeable affect for streaming? Any good guides that you would recommend to me? 

Any advice is appreciated, even if you don't answer all of the questions.

Thanks so much!