With that CPU there is no use for the extra RTX GPU. The Quicksync unit in the cpu can handle the video transcoding just as well.
Still, don’t expect more than one 4K transcoder stream with HDR to SDR tone mapping at once.
Easily your 5 users. Still, you want to avoid HDR unless most devices do support it.
(As long as you don’t select the audio track in “DTS-HD MA with Atmos” as your default audio track. Because transcoding this will take a toll on the CPU as well and cannot be accelerated with a hardware unit.)