PowerApps web part
I know the PowerApps web part is only in preview but it does seem to be working generally okay.
However, I have a significant barrier to using PowerApps because keyboard users cannot get their focus inside a PowerApp embedded on a SharePoint page.
As a standalone product, PowerApps is doing a pretty good job at meeting WCAG. But as soon as you try to use it for content in a SharePoint page it causes the page to fail WCAG, because the keyboard users cannot get their focus inside the embedded app.
I haven't tested the embed web part, but potentially this will have the same issue.
Please prioritise making sure content within web parts, especially PowerApps, Embed, Stream etc can be accessed by people who use keyboard strokes to access content.