QP is the same across all encoding technologies.
Looking at the
documentation, "Used by the Intelligent Constant Quality (ICQ) bitrate control algorithm. Values are in the 1 to 51 range, where 1 corresponds the best quality.".
It turns out that 255 was a valid QPI (
ref). I imagine it'd give horrible quality though.
Since you have a filesize in mind, are you sure that you don't want an average bitrate?
The calculations are =(8000000*GB)/NUMBER_OF_SECONDS, for instance for 5 GB and 2 hours: 8000000*5/2*60*60 = 40000000/7200 = 5555Kb/s (as a total bitrate, subtract the audio bitrate to get video bitrate)
Davinci Resolve Studio 20 build 49, Windows 11, Ultra 7 265k, Nvidia 5070 TI, 576.80 Studio