You probably already know that your (AMD) FreeSync monitor needs to be paired with (AMD) FreeSync GPU or your (NVIDIA) G-Sync GPU needs to be paired with (NVIDIA) G-Sync monitor. Your mismatched pairing defaults your GPU and monitor to generic V-Sync.

You'll get (and should solicit) many opinions about the value of FreeSync/G-Sync.

I'm of the opinion that G-Sync is vastly overhyped, overmarketed, and overpriced. It reduces tearing (and other display artifacts caused by incomplete rendering) by reducing fps: basically slowing things down until busy GPU(s) can catch up. I find the illusion isn't really worth the intermittent (slightly obvious and sometimes annoying) fps throttling it causes - especially since its real value is in hard fps gaming (vs hard fps opponents) where the last thing you want to do is run your game slower than your opponents - and the reality is that you need a combination of overworked GPU(s) and saturated PCIe bus and loaded DP bandwidth and high fps (at the threshold of your display's capabilities) for screen tearing to even occur, it can happen with some frequency in heavy games but not frequently enough to justify constant ultra-quality-enhancing performance slowdowns.

G-Sync is also incompatible with ULMB (and a few other technologies) which act in their own ways to improve display quality, so it's really a question of tradeoffs when you're pushing things hard enough for G-Sync's limitations to activate. Interestingly, FreeSync does not suffer from as many of these limitations.

(NVIDIA's G-Sync has now been reverse-engineered, analyzed, and increasingly criticized. It appears to be little more than a DRM-laden, patent-locked, and license-controlled proprietary implementation of AdaptiveSync, with technically interchangeable performance parameters when compared vs AdaptiveSync/FreeSync.)

VESA AdaptiveSync is a de-facto standard (becoming an official standard) anyhow, and is (or will be) fully compatible with existing/future FreeSync DVI/HDMI/DP interfaces. Most existing monitors and GPUs could support AdaptiveSync through firmware updates. It also turns out that many "hackers" and "experts" release these firmware updates into public domain.

Your MG279Q is rated 4ms 144Hz (it should display 144fps~250fps without tearing), and your Titan Xp is currently the fastest GPU card on market (it shouldn't cause tearing unless it can exceed 144fps~250fps, lol). Depending on what games you play and what fps you achieve, you might not ever "see" G-Sync/FreeSync displayed anyhow.

It has been argued that G-Sync is absolutely and utterly the best. So if you must absolutely and utterly have the best then you need to have a G-Sync monitor and G-Sync GPU. G-Sync monitors invariably cost a lot more (because of the cost of G-Sync modules, only available through NVIDIA), AdaptiveSync/FreeSync monitors tend to cost only a little more. All other things being equal, I think you'd see better graphical quality and performance by spending this money towards GPU card(s) before monitor.