Confusion over using decoders and encoders

[dooley2009]

I have been on a quest to accomplish one thing.... and I can't figure it out.

I want to find the best decoder to use when I am using FFmpeg and x265-10bit.

I convert x264 8 bit videos into H.265 HEVC 10 bit. I am trying to speed the process up as much as is possible and maximize the quality as that is more important to me than space. I'm sure someone will tell me that i am wishing for the stars here but I didn't know what to do at this point and really need help.

I have been running into a lot of encoding errors for example using this CLI

ffmpeg -y -hwaccel cuvid -c:v h265_cuvid -i <INPUT.mp4> -c:v libx265 -cq 21 -preset medium -profile:v main10 -x265-params sao=0:deblock=0:interlace=0:input-res=1920x1080:range=full:colorspace=rgb -c:a aac <OUTPUT.mp4>

I keep picking decoders and encoders that do not get along and i get all kinds of error codes. I really don't understand where I can go to research this exact topic. It is safe to say that I am under the impression that if I find a good decoder to use that it will speed up my efforts. Please correct me if I'm wrong.

Can anyone give me some direction and any opinions that you have on what is the current (today) top encoder and decoders?

Thank you in advance.