Nvidia Control Panel>Manage 3D Settings>Program Settings>Final Fantasy VIV: A Realm Reborn>Texture filtering - Negative LOD bias: Clamp

This should eliminate about 90% of the ground texture shimmer, and a good bit of the tree/foliage. It's an old trick that got forgotten as Nvidia had disabled the feature for quite some time but brought it back....eh, a coupe years ago? Give it a shot anyways, it's working well on my trusty GTX1080 @ 1440, and my 1070 equipped laptop.