Hi totally,
Relaxation is definitely very important. The entire playing mechanism has to be relaxed, particularly the wrist. The one exception to that are the fingers--they must remain taut at all times for articulation, whether in curved or flat position, depending on the nature of the music being played. Also, if your shoulders creep upward (a common problem), you start to feel a pain in the base of your neck from that tenseness--an instant reminder to lower your shoulders to a relaxed, natural position. Before long, you'll be doing a self checkin--"Are my shoulders rising up?" And you'll be able to consciously control that problem. After awhile, the problem will disappear as you then subconsciously keep your shoulders down, having formed a new and correct habit.
There is also a mental relaxation. Practicing and performing involve thinking analytically, no two ways about it. You need to be actively planning for the measure ahead to execute certain important details like voicing a chord, apply portato touch, holding a pedal point, or whatever. In so doing, sometimes one can produce a precise performance--which... sounds academic with a lack of sponteneity. On the other hand, a pianist might let go of the cerebral element to completely relax and to capitalize on the expressive aspect of the interpretation, which... can then become excessive, idiosyncratic or in bad taste. I'm talking about such things as exaggerated rubatos, uneven tempos, vague rhythms, taking too many liberties with the score, etc. resulting in loss of the structural integrity of the piece. So performance can't be strictly academic thinking nor total emphasis being given to "feeling" the piece. It's always a judicious combination of the two. I think you're on the right track!