I do agree with you on the runs that last less then a second they make no sense and its just lets see who can have the game end faster. the only runs i have watched are 2_snek's science run and some of the other science runs when i first started. non of the other categories are fun to watch cause they just kinda end. there's no real investment for a runner or watcher of the run. if the whole thing lasts less a second. this would change if it toke some skill to end the game that fast. like some crazy fast movements and inputs.
the deity dash thing i love the idea but i will probs avoid the category since i cant even beat the game on that difficulty. but it will add some much needed diversity to the runs so we can have more runs that last more then a second.
and for your first point. yes there should be a rule for showing the setup screen before hand or even just make it as a community rule (non official rule that every has agreed should be a thing).
these are just my opinions on the matter but I'm just a runner of the game and not a mod.
added note from me personally we need mods on here that check this leader board more often since some runs can take up to a month the get verified or even looked at. I've seen smaller games have more active mods. but that's just a personal issue i have