Pre COVID, the “late” sales moved to maybe 30 days out and it seems that if there’s going to be some last minute sales, that’s about when you should look - somewhere between final payment and about 30 days out.
I think that is usually limited to the times around the glacier and sailing in/out but I guess if folks are willing to pay it, they keep that price all the time.
The pay sessions ($19) are on sea days, the free ones are on port days. The same with Ripcord. No need to pay for either venue - the free version is plenty good enough.
Both the Compass and the app could be out of date with the reality on the ship, but they are accurate most of the time - you won't know for sure until you show up.
You will get all the photos which include anyone in the photo in the cabin in which the package was purchased. If there are any photos in which only the folks in the other cabin appear, you won't get those photos.