Oh sorry I have no idea how to optimize rpg maker files! ðŸ˜
I think if you use MV or MZ you can just delete all the files that a game doesn't use(in case of Atarassia it would be almost all of RTP files, about 300 MB). When finishing your project you have an option "delete unused files", or you can find them and delete manually. I'm not sure myself though, i'm using VX Ace, it always requires RTP to run.
UPD: yes, it works - i removed folders "audio" and "images", and the game works as usual. Now it's only 475 MB, and can probably be even lighter:)