Shadows, antialiasing, 3d grass and stuff like that, there's an option for terrain resolution I guess, something from 240p to 1080p, lowest option makes ground almost flat and the highest makes it detailed, but lowers the FPS, well I chose every possible setting there, but nothing did anything good or worse.
There's the technical parameters box thing that opens when you press T inside a truck, I tried each and every thing there, tried setting it to default (also tried setting graphics to default btw), but nothing.
Then I went to the sky with the camera, spawned a Cessna and while the Cessna was in the air, it acted extremelly weird, for example I was going slow, kind of stalling, I pressed the down key to make the nose go up, but instead the entire Cessna started going up, like it was a VTOL, like something was pushing it up unnaturally, so whatever it is, it's not just ground related, might be something about my hardware then, maybe the GCN 1 architecture of my GPU, I know that Blender doesn't work with GCN 1, but it works with later gen AMD gpu's, so who knows..
Also, not sure if important, but if I select the gravity option on the camera and move around the map, the camera follows the terrain perfectly, so if camera is limited by the collision, then collision isn't the issue here.