Where can I find and download the image file?

I know this place isn't for distributing Hackintosh files but I really am confused rn. I can't find any files or the ones i find are kind of oversized (like 13gb) (I am talking about Big Sur btw). Is that much of size ok? Can I write that much of data into 8gb's usb (I am asking that cause I want to make sure that I should buy 16gb of usb). Thanks in advance.

Author: @selalepark