Because the game only lets us have one save file, how are PC players meant to speed run this? I've seen people mention on reddit threads the idea of cutting and pasting a save but others have warned that Easy Anti Cheat may not like that. Does anyone know whether it's safe to manually move saves back and forth to have one "casual / completionist" save and one "speed running" save since we're only given the single slot?

I guess another option on steam is to make a dummy account and add it to my steam family but that seems silly.

I've been swapping save files with no issues, but I did turn off EAC according to this:

https://steamcommunity.com/sharedfiles/filedetails/?id=3485522937

I haven't turned off EAC, and making a manual save backup (reminiscent of Checkpoint for 3ds homebrew) works great. I've got two saves I can switch between with no issues; it just takes a few minutes each time.