I'm not talking about hardware. Hardware cheats could exist too, like in the video of the lego-mouse. I'm also not talking of lubricated keyboard switches, spring resistance or such. I'm talking about software. If it runs on your mouse it's called firmware. If some software on your OS post processes the key-hold to a key-tap it's also software. You get a advantage here by a piece of software. It's different than a benefit by having a bigger monitor, faster pc or adjusting the cpi value of the mouse.
One of this auto clickers is called razor turbo mode.
Some games that names the cheating cheating runescape, ea, minecraft
The razor users themself in their reddit says its ok (2 users)
Not everything need to be explained that it's cheating. If you have a person sitting in the room spectating and telling you game information that's also cheating, although no one specified it somewhere here (afaik). But it might be a idea to create such a site for rules of fair-play.