with stratosfear (or probably without stratosfear if you don't have a skill issue like me) you can get over certain doors in order to get to trap town and unlock red stars without actually having any stars. i'm curious about how this would factor into speedruns - would you include that "setup" in the run time, or would the run start after you set it up? would it be a part of any%, or should it be a separate category entirely? apologies for my lack of knowledge beforehand

This is actually done if you look at the 80 Star Legacy Any% Enemies Normal category. It is allowed in Any% and the time taken to activate red stars is included in the speedrun. I am guessing that the reason CarlIsBored did not do it in the current Any% category is because he either did not know about it or could not laugh clip consistently.