Sorry, meant to answer this last week! PNGs work very well in the Avid. They do carry an alpha channel. What you’ll be creating is a PNG image sequence. Before exporting, create a folder for the sequential images. When you import into Avid, check the “invert alpha” option as well as the “automatically detect sequential files”. Highlight the first file in the sequence and Avid will create a video clip from the sequence.
I’m not sure how to answer your anamorphic question.