No hand tight then tightened 3/4 of a turn is enough , if you strangle it to death you crush the olive onto the pipe this can cause it to fail , a smear of pipe jointing compound around the pipe before sliding it into position and tightening is the way . Kop
It may start to squeak at about the right tightness, but only if you install it dry. And if it doesn't squeak and you keep tightening anyway, then you'll overtighten.
No hand tight then tightened 3/4 of a turn is enough , if you strangle it to death you crush the olive onto the pipe this can cause it to fail , a smear of pipe jointing compound around the pipe before sliding it into position and tightening is the way . Kop
The seals on a compression fitting are tube-olive and olive-fitting. The threads aren't involved, they just provide the force needed to hold the other parts in place.
As above the seal is made internally between the pipe, olive and the fitting the thread is just to keep it together and tight and does not come in contact with the water. Regards Kop