I've noticed that some guys with massive wrists can generate a lot of power in their smashes from just a subtle wrist movement. Is this from their technique (their technique was really good) and/or wrist size? I ask this because I have small and somewhat weak wrists and I often resort to using body rotation and proper elbow movements for a decent smash. I'm a decently built guy for badminton with lots of upper body and lower body strength. Let me know what you think!
It's the technique, not the size of their wrists. Even the size and strength of your forearms will play a minor role compared to the quality of your technique.
Best example I can think of... Ratchanok Inthanon can probably hit smashes harder than you and me, despite her having wimpy wrists and arms.
I have a small wrist, palm and short fingers. However, in my early days in school and in 20s, I used to have a very powerful smashes, even spar with few national players who find my smashes too strong for them so much that they have to move backward to take my smashes. But that was then.... Now I am already in my 50s. However weakened my strength and power is, I still pack some power though for my peers. Still known to them with powerful smashes. However, given my age, how much longer and how many times do you think I can still smash? It is all about technique, get it right and you will find that even you weaker smash means something to your opponent. Often a miss-hit smash can prove to be fatal to score points instead of hard smashes. Smashes alone may not always win you points, but intelligent play varying the intensity of your smashes do give you additional option to score points in the game especially if you are a hard smasher like I used to be. I only learn that much later.