I'm not 100% sure, but I think the shops on Main Street stay open for about an hour after closing. We've also spent a few minutes doing photos after closing but not sure how long that lasts. I'd guess you probably have at least a couple of castle photo ops on the way out, depending on how late it is. I picked up some tea in January after closing and the shops were pretty busy.
DHS - we had a late Oga's in January, and they were running behind and didn't get us in until after 8 p.m., so we came out around 9 when the park closed at 7 p.m. We were given a personal escort! (It was fun chatting but clearly they didn't want lingering) and once they brought us "off the planet," other CMs ushered us out of the park around every corner. Everything was definitely shut down at that point.
Edited.I forgot to say congrats on the ADRs!! That's awesome