Like many modern 2D animation and compositing programs, Moho has a basic 3D environment for animating the camera and placing/animating 2D 'cards' in a 3D space, but its focus is primarily 2D animation. And while Moho does allow you to import 3D objects via OBJ, what you can do with the OBJ is pretty limited.
If you're intention is to import a 3D character and rig it in Moho for animation, you're going to be disappointed because Moho is not meant to work that way. For Moho, you're better off rendering images from your 3D program, importing them as bitmap layers and then rigging that as a 2D puppet. I do this occasionally, and the new Mesh tools in Moho make this process easier than ever.
For true 3D character rigging and animation, you need to do that in a
dedicated 3D program, like Maya, Lightwave or Blender. (The 3 programs I'm most familiar with.)
Blender is a good choice and I recommend it. I've been using mainly LightWave since the 1990's and occasionally Maya, and recently I started transitioning to Blender for 3D animation. Though my experience with Blender is mostly recent, I have to say this program has come a
long way in just a few years. As you probably know, Blender has a unique 2D drawing system called Grease Pencil, and the results can be rigged like 3D objects because every stroke in the drawing is actually a 3D object.
Working and animating with Grease Pencil is quite different from Moho, and I do not anticipate using Blender the same way I use Moho. As a 2D puppet animation program, I think Moho is easier to use and far more capable, but as a companion program, I feel Blender can offer different possibilities than I have from working with Moho alone.
In fact, many of the projects I work on tend to mix Moho animations with other 3D programs, along with a compositing program like After Effects or Fusion, so adding Blender to my tool box feels completely natural.
Re: FBX, I do wish Moho gets more I/O development love in the future. To transfer camera, object, bones and layer data between a 3D program and compositing programs like Nuke and Fusion, I typically use FBX, and Alembic for point displacement animations. But After Effects is a bit of an outlier; it's not natively compatible with FBX or Alembic, so other methods are needed for getting 3D data transferred. Moho has options for getting 3D data to compositors but it's limited compared to what I have available in the 3D programs I use.
That said, Moho has some really good tools for faking 3D animation. If you look at
my 2019 demo reel at around 2:08, there is a truck that appears to be 3D but this animation is actually a flat 2D vector-paint hybrid drawing I drew, rigged and animated in Moho.
The sports car, on the other hand was modeled and animated in LightWave, with the 2D characters drawn and animated in Moho imported to LightWave and parented to the car in LightWave. The winding road environment was painted in Photoshop and put together and animated entirely in After Effects or Moho, so this is another good example of using multiple (2D, 3D, painting and compositing) programs together for one final result.