If you are buying a G-sync monitor at this moment, the only input option is Display port, no other inputs are available.
If you are going to use Freesync, you can expect other inputs other than the mandatory display port.
G-sync monitors command a premium and will be well over 5K, too bad Acer is not available here if not we would have more options.
Anyway, there are a slew of new G-sync and Freesync monitors coming up from Asus, Acer,AOC and Dell. With the upcoming G-sync monitors, you can expect a HDMI input in addition to the display port input.