I'd say on the larger side of medium. The way I hold it I use my index finger for both L1/2 and the curve on the back (of the controller) makes it that I need to shift my grip when I wanna switch between them. I can hit the corner of L1 with the last knuckle, but it feels kinda off to do that.
I have the old NS09 (KK Pro) and NS39 (KK3 Max). The dongle latency is on par with bluetooth, which is not great. https://gamepadla.com/gulikit-kk3-max-kingkong-3-ns39.html