May seem like a basic question for some, but not for me, thanks a lot in advance!
It's usually 2mm. Hyperx's own red switches have a 1.8mm actuation distance, but both are practically the same.
I suppose feathertouch means easy to click without much force needed. I've never heard of feathertouch either. Perhaps the keys found on laptops or as mentioned earlier, LP keyboards are what OP means. I recall Roccat having an LP keyboard. Only for the keycaps though, not the switches.