You need a torque wrench. It’s as simple as that. Modern hardware tolerances and lightweight parts don’t let you get away with close enough. If you are changing a stem or working on suspension pivots, seat post clamps, cranks or almost any bolt on a modern bike use a torque wrench to tighten the bolts! Bad things happen when bolts are not done up tight enough and there is nothing like the feeling of seeing an expensive part crack, snap or strip because you just overtightened it! Own a torque wrench, read the torque specs for your frame and parts and have a long happy relationship with your performance bike. You only have to NOT break one single high end part and it’s paid for itself already!