I can confirm Roger's answer as I am trying it now, 100% CPU usage with no GPU encoding using MagixAV1.

Thank you both for the fast an clear answers. Then voukoder could be the solution until VP supports it.

Here is my comparison of V22 rendering a H264 4K 5.3min project with fades and music:

MagicAV1, 4K template ave bit rate 40Mb/s, max 75MB/s. Rendered = size 1.5GB, time=6.31s, speed= 21fps, overall bitrate=40Mb/s

Voukoder AV1 NVENC Variable bit rate 40,000/Max bit rate 75,000, Muli Pass Full, Slowest rate-max quality.
Rendered = size 1.6GB, time=3.42s, speed= 36fps, overall bit rate 42MB/s

So Voukoder with GPU is twice as fast as CPU i9-13900K

I can also add that I've tested Voukoder with a 4090 and it renders av1_nvenc fine. Worked the same with vp19-22 which I have installed on the same machine. Should work just as well with vp18.

@Howard-Vigorita could you post the settings you use for 4K max quality. thanks

I while back I compared nvidia hardware renders on my 4090 via Voukoder with the vp22 default Magix av1 renders which are slower and cpu only. I still have the clips laying around. The reference clip I used was the one in this thread in which artifacts were seen in the Magix render. The test wasn't to find the absolute best quality settings, but to see if Voukoder got rid of the artifacts. And it did. And objective quality analysis confirmed that the Voukoder Nvidia av1 renders yielded better measurements overall. But more to the point of your question, the 3 different Nvidia render strategies in Voukoder all yielded similar results at comparable bitrates with vbr marginally on top. I just ran the clips through ffmetrics again and this is what I got:

Luckily I also saved the Voukoder settings I used in presets. Here are the dialog screens:

Just keep in mind I used @RogerS's clip as a reference which was 100 mbps avc from a camera and all the renders were matched to the 8-bit bitrate of the current Magix av1 default for comparison. If you set Voukoder to 10-bit output and raise the bitrate, quality will increase across the board. I usually prefer vbr or cbr so I can get the highest quality through a given transmission bandwidth for broadcast or upload.

Also keep in mind that if you use a higher quality, higher-bitrate input clip or do lut, fx, or media gen inside Vegas, quality will become more of a function of other internal things besides render settings.

Thanks Howard, in my clips I have been trying out I have my grandson running across a sandy beach towards the sea and back. With Magix AV1 I see some artifacts in the rendering of the sand which is not present in the Voukoder H264 and Voukoder AV1 render. The other thing that caused a massive increase in rendering time was in my full 27min project I included some clips taken on my iPhone SE (HEVC) which dropped the encoding speed from 32fps to 0.5-1 fps for those clips.

Btw, the Intel SVT encoder has also been observed to create artifacts with both Voukoder & ffmpeg. I suspect av1_qsv rendered with an Intel Arc would be similar. Av1_nvenc seems to be the best of all worlds.