From what I gathered it’s usually setting up a base that makes your computer work hard and get down from 60 ups.

Not always but honestly that’s how I personally see it. When it’s so massive your computer is having trouble running it. Of course that’s immo

Pre 2.0 the general consensus for what counts as a mega base was at least 1000 spm (science per minute), I think.

Well, mega as a scientific notation is 1,000,000 so that is your starting point.

All pre 2.0 Megabase should be renamed to kilo base as the are between 1 thousand and one million.

But who so big before going to another planet? The big mining drills will reduce your ore consumption by half and furnaces have a built in productivity of 50% saving even more ore.