UHD to 1080p HDR

[Haxxon]

So I have an Optoma HD27HDR which takes a 4k signal but outputs 1080p with HDR. My 4K encodes are just too intensive for my Plex server.
What I could use help with is understanding how to get the best 1080p encode from the 4K disc/file.
2-pass High Quality with bitrate cranked up? (how high?) vs. CRF (20? less?)
Any advice much appreciated!
thanks

[Mona]

UHD source 50M~80M, try use 1080.hevc.10bit two pass with 15M~20M bitrate or CRF 20.