So I made a Win32 build, “shipping”/“production” build configuration, and the hitching is just as bad, subjectively even slightly worse, than in-editor… how odd! Considering this mid-2014 model is one of the fastest mobile workstations around (all specs maxed out and no energy-saving etc enabled), and considering I have nothing but a 3rd-person pawn, a sky, and streaming landscape tiles without foliage all sharing nothing-but-a-single-grass-texture that’s supremely discouraging… no custom code that could slow things down, nothing but raw UE4.6 starter pawn and some world-comp/streamed landscape tiles.
Uploading a copy of the project to here (5GB just for heightmaps? oh well 
in case anyone ever wants to check it out…