For example, one thing I've been wondering about from the physical side is whether my bokken is simply too light to practice with?
I don't have a lot of answers but one thing I STRONGLY believe is that it cannot be too light in the beginning. Borrowing a cheap chinatown very light bokken was very illuminating for me.
A variety of weights of bokken is nice, and you can feel different things with different weights, but I think the most important thing is to have a light one.
(in some ways heavy ones are too forgiving, and in some ways light ones are limiting.. I'll stick with my light one for a while.)
I think the reason is if you are trying to do things with as much relaxation as possible (as little muscle flexion as possible) then the light one lets you get less in your own way.