So I got all the regular stars and flags and stamps (despite a few still missing) from all the normal and bonus stages in Super Mario 3d World and it ended up not being that bad as I stretched it out over a decent stretch of time and just googled where some of the tricky ones were hiding.
It turns out there were only three stages in this last section, one being what appears to be a stupidly long mystery house battle arena thing and another being a Captain Toad stage. Basically there is only one actual regular stage here so… hopefully it is a decent one?