I just found out that apple prores 444 alpha still has issues. when I render it cuts the right and bottom side of the video, simply. And that doesn't happen with quicktime, but vegas quicktime doesn't work in premiere besides generating very heavy files, so I need apple prores.
Yes, Can confirm, the apple prores 444 alpha channel is basically non functional. There are limited options in getting great alpha channel output at small file sizes that is compatible across all platforms.
I love MagicYUV speed and its alpha channel functionality, but man, the file sizes are enormously huge!