Granted that you thought ahead re: mountain placement - you still haven't depicted anything much in other topography. You *can* decide on a coast then figure what lies just inland, that just seems backwards, and could lead to subtly implausible arrangements. For instance, the sunderings are your only high land approaching the sea. -- real mountain forming processes often happen near coasts - colliding tectonic plates, for instance. True enough, some will be mid-continent. I could imagine the Sundering Mountains as the seam where two plates are colliding, Himalayan style. The other ranges could be leftovers of older uplift events or patches of volcanism. Other than that, do you plan any hills/ plateaus/ rough territory near the sea? For instance, is there even a modest spine down that lower E-W strip, separating the gulf/ bay complex from the southern ocean? If there is, wherever it lies close to the sea, there'll be different coastal geological processes going on. For that matter the character of your sea floor is going to make a huge difference. Broad shallow gently sloping coastal shelves would make long swooping beachy shores plausible, or highly indented swampy delta/ bayou country. But one would expect a more fingered set of sharp ish indentations if the coast falls away more sharply - say with the drowned mountain fjord systems of Scandinavia or the drowned hilly character of the US DelMarVa Peninsula / Chesapeake Bay.