load a cheat from usb drive -> Software runs in your pc's memory, no point at all, except that the file itself is no longer on your computer. But anticheats have moved past that like half a decade ago. They analyse memory, not files(they can ofcourse and do, but its low hanging fruit, the most basic hash detection).
load a cheat on second pc and use pci-leech + fake driver to read memory -> cheat software does not run in you own memory.
not sure why you talk about "loading" a cheat in combination with a mouse, if you use something to "load" a cheat, then it runs in your memoryspace, defeating any purpose of using hardware in the first place. You can put something between mouse chip and your pc, but that would be the same as using an external device like arduino and the detection vector would be the same. The driver/firmware would be customized and can be analysed by faceit/esea(and will be when you reach high ranks) and get you banned, same with pci_leech.