The RAID controller will work fine as a general disk controller, but understand that UnRaid does not support RAID of any type. If you wish to use UnRaid you will sooner or later need to copy your data off your old RAID array and in to UnRaid.
Dockers are really the way to go with UnRaid. I have a similar system to the one you are looking at with 32 cores. I assign 8 cores to my Windows 10 VM, 8 cores to my Plex Docker and 8 cores to the rest of my dockers, they include Couch Potato, Sonarr, Crash Plan & NZBget amongst others. The whole setup just works. Couch Potato, Sonarr & NZBget take care of automatically downloading Movies & TV shows and the Plex docker has enough grunt to stream them all around the house as well as transcode for clients outside the network.
As far as the 2 gaming VMs go, you don't need any extra technology as it's already supported in UnRaid. You will need to make sure that UnRaid is setup to use your onboard VGA and then each of your VMs can have a GPU each.