Hi and welcome to AllNurses
The degree requirements for a clinical instructor will vary from state to state, and from program type to program type (i.e., ADN versus BSN) but the very minimum educational requirement is a BSN (for some ADN programs in some states). For classroom instruction, again, it depends on the state. In most states, a minimum of a Master's degree is required. However, in some states (such as NC), one can teach nursing in a classroom (in ADN programs) with a BSN. You really need to check with your state BON as to educational requirements.
And, no, you don't have to be a "drill sargeant" to be an effective clinical instructor. Research has shown that the most effective instructors are the ones who have high standards, yet connect with their students in a caring way. The drill sargeant model is "old school" and fading away for more student-friendly approaches to teaching nursing.
The following members say Thank You: