The "prores_ks" encoder can only be fed with 10 bit data. So even when it outputs 8 bit data. Yes, confusing.
Thank you for the explanation. Do you have plans to implement a ProRes GPU encoder?
I have fast video card (RTX3070) and an old CPU (i5 4670T), so my CPU encoding is very slow: I got about 1-3 fps when export to Prores using Voukoder (meanwhile, I got 25-30 fps when using Davinci internal h.254 GPU encoding with the same clips).