Hi Philip,
OT uses a variant of quadrilateralized spherical cube projection internally, but it processes external datasets in common rectangular geographic projection, divided into tiles. It creates all levels of detail and takes care of everything from that. The problem is usually how one can prepare the source data for it.
While the 1km resolution can be used, you'll soon notice that the results don't look nearly as good in real view, as they look on a 2D or relief map, and considerably more detail is needed. At least 100m would be good, but possibly coarser is still usable.
Biome data (colors and vegetation density) are currently in 500m resolution.
Usually the problem is that there are but a few tools that can work with large datasets, and it takes them ages to process it, and the results of various erosion algorithms don't look good anyway. What ME-DEM folks did in the end was that they took real-world mountains and synthesized the mountains in M-E world from that. FYI, their complete workflow takes approximately one week, and that's just processing relatively small patch of terrain, just as large as the Europe ...
Once you have these data prepared, processing in Outerra is fast - less than hour to process whole Earth in 90m resolution (raw ~200GB), the tool does the reprojection + wavelet compression and generates dataset suitable for the engine.