It looks like there's no anti-aliasing for the alpha channel which makes jittery edges:
The solution I now use, is exporting video with a green background and use the keyer in fcp to get rid off the backgrounds:
Will there be anti-aliasing for png sequence exports with transparency?
what if you double size for export?
and/or even produce with double size ...?
Tried it, helped a bit. But the client wasn't happy about it. The work-a-round still works fine, but it doesn't feel good to add a background and use a keyer to make is disappear again 
using a hypeshape only seemed to work well for me ...
is it a image that shows the jittery ?
Yes, you're right. Hype shapes works fine, ijittery edges is only with images, tried svg and png.
I'd be curious if you see jittery edges when unchecking 'automatically optimize when exporting' for your image. (If you can share your image giving you trash edges it would be helpful for us to test this)
Just checked it with 'automatically optimize when exporting' unchecked and this doesn't resolve this issue. The hype document had a bit of a big size in MB's because there was a video in it. I swapped the video for a still of the actor, now the file size is acceptable 
PiP - DT part1-jittery-edges.hype.zip (2.5 MB)
I get great results when exporting as a PNG sequence and dropping that into FCP:
I've just tried with a few other options but still no luck
Maybe it's my MacBook Pro M1max. There's a issue with all M1max/pro/ultra with transparency and video: discussion on apple forum.
I'll have a look if i can get my old intel macbook back from my son and give it try with that one...
I'm curious though how you put a png sequence in FCP? I use quicktime pro (on a non M1pro/max machine) to convert the png's to a quicktime prores444. Or do you use animated png?
Drag and drop the images, make a compound clip, then retime the compound clip.
I’m on a M1 (not max)
I had to work on 20 episodes and just finished them. So now I finally have time to get back to this topic. I've tried every option that you guys mentioned and updated to latest versions of Monterey, video codecs etc. It now works like a charm!
