I did a lot of testing in exporting in different formats (PNG, JPEG, PSD, etc) and ways - I think it's exporting at all through Clip Studio that adds that weird white pixelation, and from there it can get a little confusing on how to fix it since I don't recall if it's fixed by re-exporting in Krita. For some reason, Paint works? At this point, because a lot of my art friends use Clip, I just open the png file in Paint, hit ctrl s, and then close paint to get rid of the border on every piece one by one. If you find an easier way to do it let me know!