Thanks for the response. I browsed help articles beforehand and couldn't find this specific case anywhere. It might be good to update the following article with the information for others to come.

I've run into something I haven't quite been able to figure out how to solve. I've selected NVENC HVEC as hardware acceleration, but the majority of my recordings (both regular and TimeShift) still end up being recorded with H.264/AVC. Only every now and then does a file appear to be truly encoded a...