Underclock, hardmod (better tim, more holes), ac
you could use sys-clk or freebird to downclock the cpu/gpu to lower power usage which in term lower the temp. but i wouldn't worry to much about it. its normal for it to warm up on games that put it though its passe
the only thing that would make the Switch run cooler/reduce temperatures is to undervolt the system or doing some repasting with new thermal paste/liquid metal
To be fair we have seen hacks before to portable games (example http://www.dwedit.org/dwedit_board/viewtopic.php?id=480 ) that change some things about the game's code to cause them to use less CPU and throttle down better) and for all I know the makers of the OP's game of choice were a bunch of crack smokers that made poor choices (ask anybody that handles either making "backups" run, does ROM hacks down to assembly level or otherwise has cause to look at code about the general quality of code or notable howlers they encountered) in their coding.the only thing that would make the Switch run cooler/reduce temperatures is to undervolt the system or doing some repasting with new thermal paste/liquid metal
Any software mods out there that can undervolt?