Dedicated GPU HW transcoding is going to be far faster than CPU HW transcoding.
It also depends on the CPU. Between my 4th gen Haswelll i5 and a RTX 2060, it was like 1:1 on the CPU (1 hour of video takes 1 hour to transcode), and 3:1 on the GPU (1 hour of video takes 20 minutes to transcode). For comparison, CPU transcoding of a 3-hour HD show takes about 8 hours to transcode to AV1. But I have an ancient CPU, so there’s that.
It also depends on how much video you’re recording and transcoding and how long after recording do you need it transcoded to H.265. For me, I can let it run all night while I sleep and that’s good enough.