So, I decided to really, REALLY stress the M1 out. I copied a concert locally. The test video for this is Hans Zimmer's concert in Prague. Its a 1080p H264 video with Dolby Atmos and a bit-rate of 35mbit/s average.
I opened a browser, hit the Plex, and started up the concert. for each one, I set the transcode to 720mbit/s 4Mbit. And then I kept repeating it. And it went ON and ON.
Till finally, on the 14th transcode, I finally hit the CPU's limits. It stopped at 13 transcodes.
For reference, the current Intel machine I have to test for work has a i5.-10400, and it gave up the ghost after 3 transcodes, didn't even start the 3rd.
My old 2013 i7-4790k can do 9 transcodes in CPU.
I've never tested the Ryzen (but I think will for laughs). I bet on pure CPU it'll match the M1. I may also enable HW transcoding and see how many the 2080 can do, but I think Nvidia put a limiter on the NVEnc encoder that might limit me to 4.
The M1 is a serious desktop processor. Even if its low power, Apple has built an amazing CPU.