itch.io

If you want to do a quick and dirty solution, write a launcher to configure things like image cache sizes and various other settings.  Some quick configuration tweaks and suggestions given detected hardware resources should provide an adequate performance boost.  Reading O'Reilly's High Performance Python couldn't hurt, and there are some Ren'py performance guides too.  When in doubt check out what the Eternum Dev is doing.

Was this inspired by Ikari Warriors on the NES?  Because it plays a lot like Ikari Warriors

This looked interesting, but I've suffered from seizures the last couple of years and the beginning makes this completely unplayble for me.