I subscribe to feeds by just copying the human-readable url (right-click on the channel's title). When I embed the videos from these channels only the long videos are embedded, the shorts are not (has to do with a different url for shorts). So no problems here.

I do have a problem with old videos getting presented as new videos. Videos from weeks ago get a publication date of two days ago. Sometimes I just don't know - based on a thumbnail - if I've already seen the video.