Build help for Unraid/Plex server with VM Win/OSX

I currently have a Synology DS1019+ that is storing my media and running my Plex, Sab, and Sonarr/Radarr. It works great for the media acquisition and storage but the Plex lags a bit so I would like to dive in to building something that can replace it. I would like to use unraid for the OS with the ability to create a VM for windows and possibly OSX. I have a handful of family that use Plex with various hardware so being able to have a few transcodes going would be helpful. I have Plex pass so the DS is able to transcode using QS.

Not sure if it is better to buy and assemble or if there is a decent prebuilt that would suit me needs. Anyone have experience with a system that is doing something similar to what I am wanting to do? Any ideas would be greatly appreciated.