I'm having trouble understanding when I should play with just wrist and when I should incorporate arm movement when playing traditional. I am also having trouble letting my wrist move when I use arm even when I'm totally relaxed. When I try to incorporate both wrist and arm, it feels like an unnatural movement and it doesn't feel accurate.
Drumming should be a very organic thing, meaning movements happen in a natural manner. With the exception of really big and loud passages where you have to incorporate a significant amount of arm to achieve height and dynamic or fast rolls in which you must pump your arms, your arm should generally move as a reaction to your wrist moving rather than you consciously moving Think about it like this. There's a toy boat sitting in a pond. You toss a rock into the pond and it creates ripples that travel and move the boat. Your wrist is the rock, the ripples are the motion of your wrist, and the boat is your arm. If we were to do this in slow motion, on the upstroke we would see your wrist turn and your arm move slightly. On the downstroke we would see the reverse with your arm coming back down returning to its set position, then your wrist following and playing the note. The point of your arm moving is to add mass on the top of the stick to give a fuller sound. Try removing the sticks from your hands. Raise your hand above the drum, limp, and then just let it fall onto the head. Feel how much weight your arm has. The motion of your wrist is causing this weight to move, then when the weight naturally comes back down with your wrist, it adds sound.