for reference on my windows desktop test plex server, 960gtx gm206 via windows task manager
4k/hdr/x265 decode + 1080p/x264 encode + truehd > aac (cpu)
20-30% gpu DEcode load
less than 10% gpu ENcode load
0.9/2.0GB vram load
idle gpu vram load = 0.6/2GB
so on in this case, the combined 4k decode/1080encode load is only using 0.3GB of vram.
that is hugely different than what I see on linux 4k decode (~1.1 to 1.5 GB vram/thread).