1) You can export tiled heightfields, bitmaps (splat/normal/texture/etc), and meshes.
2) The exported maps can optionally have matching edges or not -- typically but not always, each tile will have duplicate edges, and WM will work either way.
3) Yes, with some caveats; erosion and some other devices do not always perform the same in a tiled build as they do in a normal one. This can be mitigated by turning up the "blending factor", but cannot be removed completely.
I can offer a 30 day fully functional trial of the Professional Edition that you can use to see if it works for your needs. Open a support ticket at the helpdesk (http://www.world-machine.com/helpdesk
) with your name and email address to get started on that route.