Basically, you can use two of these monitors if you have the appropriate graphics card that supports at least two monitors. I don't know what g-Sync is all about because I have never dealt with it. But it should not be a problem.

Basically, yes, it works.
The only question is, why use 2 g-sync monitors if in the end you only play on one anyway? I would understand that with 3 screens. (by the way, it also works with 3 screens, but the dp connections will probably be a problem, because there are usually only 2 per graphics card and dp is a prerequisite for g-sync).
You can also run 1 g-sync and a non g-sync monitor at the same time. Everything is possible.