I've been getting into doing my own maintenance like drive train cleaning with chains, cassettes, and chainrings off the bike and soaking them in degreaser.

I've changed a few pedals and stems before and am in the process of switching to new cassettes and chainrings.

Is it essential that I follow all the torque specs closely? When I take my bike to LBS, I see the mechanics working on things without a torque wrench. It seems they just go with their feel. They've probably done it so many times that they probably know mostly what parts requires what Nm and how much force to put in their arms by feel.

I did buy a small 1/4" drive torque wrench set that only goes up to 25Nm so I use that for the more delicate parts with low torque specs. For example, my stem indicates not to exceed 4Nm so I torque it slightly below that. The lockring on the cassette however, indicates 40Nm. I don't have a socket bit big enough to fit a lockring tool so I just try to tighten enough without going too tight (just by feel). My crankarm indicates 48-53 Nm but I go up to 25Nm with my torque wrench and then use a regular hex wrench to go some more but I have no idea what actual torque it is ending up.

Are these torque specs all essential to follow and thus a bigger torque wrench necessary? How do you guys work on your bikes?

Thanks.