Landscapes use 8-bit data, and meshes use 16-bit data, and from a number of other factors it is far better to use landscape creation than meshes only in terms of memory and speed. It’s also rather difficult to sculpt meshes in UE, if needed, than it is to sculpt a generated landscape in UE. In an external program it’s easier to sculpt meshes with the right tools, such as in Blender. But UE doesn’t have extensive mesh sculpting tools that function in-editor to produce immediate results. For smaller maps in an RTS, try making smaller landscape sizes with higher resolution levels. You can even generate a 2x2, 3x3, 4x2, etc. landscape per map and select higher quads / component (little squares per big square). To get a 4x2 or 1x3, or something similar, first generate a 4x4 or 3x3 respectively, and then delete components until the basic layout/shape is created. Enable the Landmass plugin for some useful editing tools that are not available in the base landscape tools.