You could totally run them on an early 90’s PC. Just don’t try to use autocomplete plugins or anything else that needs to hook into every character insertion event. Also I would imagine git (and hence magit) would run pretty slow on an old PC due to all the hashing, but I think it would still be usable.

Also you’d want to avoid loading too many plugins all at once, due to limited RAM, but that should be obvious as well.