I have 2 different ones.

I have a 3/8 drive one that I use for cranks and bottom brackets. The torque spec for those parts is usually around 30 to 35 lb/ft. That's more than I would tighten them if left to my own devices and probably more than I can even get using only a 6" allen wrench. If you undertorque them you are likely to get creaking noises in the bottom bracket and the left crankarm is likely to come undone.

I have a 1/4" drive one that I use for stems and handlebars. I'd use it for seatposts too if I had any carbon fiber ones. The torque spec for these parts is frequently way less than what I would do on my own. The trick to keeping everything tight with minimum torque is gradually tightening every bolt evenly so the whole face plate area is working for you. Undertightening these parts results in slipping. Overtorqueing them can result in crushing expensive carbon handlebars.

I've got a lot of years experience woriing on bikes. I think that I've got a pretty good "feel" for how tight is tight. I've also been driving cars for a long time and think that I've got a pretty good feel for how fast is fast. I still glance at my speedometer from time to time and sometimes, when I do, I surprise myself.