Cpu 100% on some transcoding's. How can I fix this?

I can give you other examples they do the same as long as its software transcoding
My usage and content must use hardware otherwise it wont finish buffering forever

So the problem
Isnt the content as much as its hardware have to do the coding soo :3

Lets say i will build another plex server soon because this is my gaming pc is igpu from inte 8th gen like i5 8400 better than quadro p2000 ?
Not talking performance but compatibility wise and support for more harware transcoding with plex

Also can it handle :

3 4K transcoding to 4K
At the same time another 3 1080p transcoding to 1080p/720p

At the dame time

So like 6 total but 3 of them heavy 4k some hdr and some are not