Some things like threaded bottom bracket cups have a high torque spec and you are unlikely to tighten them adequately without a torque wrench. Others like stem bolts, particularly on a carbon steerer or handle bar, have a low torque spec and you are likely to over torque them without a torque wrench.

Get a couple of torque wrenches. A 1/4" and a 1/2" square drive beam wrenches should cover the full range and are relatively inexpensive.