All great suggestions, K2~! One addition would be to make sure you stretch and warm up before playing, as well as stretching again after you finish. Gotta keep them joints/tendons happy, loose, and warm.
Speaking from experience with it: Kyle’s bachi may be small, but that thing has some weight to it. Don’t be fooled by the size; there is a lead weight in some bachi, ideally to help ease the amount of force one needs to exert when playing. But oh man, does Kyle’s bachi have some nice flex action; makes that thing feel like butter~
That’s another thing to consider: the flex of a given bachi. Having played with a wood bachi, I can firmly say I hate them for tsugaru-style. They make playing fluidly much harder and there is almost zero flex/give. I started with a wooden handle that had bekko tips (had some flex), went to the wood (zero flex), then plastic (decent flex), and now I’m using a full bekkou-head bachi (good amount of flex). Each had their perks and draw-backs.
Ultimately, these concepts are all subject to your play style, how much force you use when striking, and taste in amount of flex and the tone it produces. Nitta-san generally goes as heavy as possible with the max flex he can get. Some people like light, yet stiff.
Here’s to your wrist’s/hand’s health, and a safer, healthier future of playing shamisen~!!