[HELP] How encode 8bit to 10bit correctly?

[Selur]

It doesn't matter whether ConvertBits(10) is set or not, right?

right

But it is better that it was?

Nope, should be the same.

Or I switch to Vapoursynth and do not worry, everything will work correctly?

Vapoursynth usually scales better with more cores, but uses more RAM, also I think it's more straight forward when dealing with high bit depth.
(+ Hybrid uses a 64bit version of Vapoursynth, but only a 32bit version of Avisynth)
Only reason to using Avisynth for me is when I use some old filters which are not available in Vapoursynth.

Cu Selur

Ps.: I send you a link to a dev version which should adjust the Avisynth script 'properly'.