A few questions

I've got a character that's split into multiple pieces, is there any way to get oFusion to export it as a mesh with submeshes instead of multiple meshes? (Without merging all the parts) Also, in the oFusion viewport, all the pieces appear at totally wrong location (eyes are far away from the head, and so on). I've tried resetting xForm, but that only made it worse.

Its very simple:

if you have an object, you will export a mesh
if you have multiple objects, you will export multiple meshes

If you need to export a single mesh, then you need to have a single object

You have total control on how the media is produced

When you attach multiple objects to create a single object, you can continue to work at sub-object level if you need (select just the part you need) and assign or modify materials independent of other sub parts)