Does VSync affect input lag in live dealer games?

Absolutely, VSync will add input lag to live dealer games. When you enable VSync, your computer's GPU synchronizes the frame rate with the monitor. That means there will be a slight delay between you doing something (e. g. placing a bet) and your monitor displaying the result. 30-100ms isn't much in most other casino games, but in live dealer games it can make a difference. And from my personal experience in running a casino, I have seen competitive online players turn VSync off completely to reduce input lag. But if you turn VSync off, you risk getting screen tearing, and many players don't like that either. Personally, I would recommend experimenting with both settings to see what works best for your setup. On the wiki, please include a note that the effect of VSync on latency varies depending on the machine and software used. Players should always check before they play.

This is what I think:

Yes, that’s correct–V-Sync does introduce input lag. It synchronizes your graphics card with your display’s refresh rate (thus preventing tearing), but introduces input lag. For live dealer games, this could be an issue, especially if players are trying to click just before the end of the round is reached. Personally, I like V-Sync off as input response is faster. However, if tearing bothers you, then do whatever you like. Your end users should try both options out on their own devices and decide which works best.