Actual setup of the unraid service - https://www.youtube.com/watch?v=CcRwT7iHIcc

Use this guide for the Radarr/Sonarr/Plex (makes it automated) - https://trash-guides.info/

For build ideas and general info on hardware that will destroy a snylogy for half the price - https://www.serverbuilds.net/

Things I will tell you from personal experience:

1) don't go crazy over a processor.. I have a i3-10100 in my build and it handles transcodes (yes, even 4k) fine. Just make sure it has a integrated graphics in the processor. This link here is a guide for how to enable it.

2) When it comes to drives, I would get case that can hold the absolute most within your budget.. I screwed myself once thinking I wouldn't even need that many hard drives and had to swap cases.. Now I have a Fractal Design Define 7 XL that holds 18.. Yes, I was filling 14tb drives that quick ( don't judge me :P )

When I first ventured down this route, I had a ton of help from these resources and Reddit. I was hella mad at this synology I spent 800 bucks on was choking on 1080P transcodes... So, hopefully this will help you avoid some of the headaches I went through.

Just got to be willing to learn and do your homework but the payoff is huge.