Efficient playing looks easy becasue of accuracy and power. Playing well takes power and direction, using as much opportunity as possible to relax - either complete release for a fraction of a second or a generally more relaxed direction for several bars. The trick is finding the balance between these two and finding out which muscles need to be the ones directing the power in the given circumstance.
My own experience, beyond working with my rheumatoid arthritis, is that there is a pain quality difference between tiring muscles and potentially risky pain. Working muscles will ache a little and tire. You need to work them, but you need to rest them properly when you have worked them and you need to build up their potential for work. Over-working causes aching for a couple of days (like going for a long bike ride or walk if you haven't ridden for ages). That ache isn't dangerous, but a reminder to take better care of yourself anda build up your efforst.
Strain on the ligaments or bones could be dangerous and causes a seizing, sharp pain. That pain is a message to stop immediately and rest / ice if the pain continues.
I found lack of strength in the hands and fingers led me to overuse my wrists. The hands are not as prone to damage as the wrists. I had to work deliberately to build the hand strength so that I oculd stop compensating by using my wrists. It improved my playing immensely - control, ease, comfort, precision, expression, etc.