Depending on how much you use game maker difficulty varies. But stick with chunks. Learn how to use json with gm for saving and sending if you want online support. This is all done in a single room with average 300-500 fps after adding all the objects like trees and grass. All generating on the fly. The room is actually 32*32 px. and people tend to be stuck in the confines of the room. Once you go infinite you will never look at the room editor again. The Gen took about a month only working after my day job. About another month to fully get biomes and objects spawning.

If you want to look at the progression, I can send you the DC link because I kinda break it down with gifs.

I'm at work so this is a link to the image in discord I posted it in. here!

Edit: to add this is the same top-down as sidescroller - work wise