Hi loveart - organic shapes tend to be difficult, stuff like you show there may be better done in a polygon sub-d modeler rather than in a CAD program. CAD programs are strongest when working with shapes that can be created primarily from 2D profile curves, and often times organic shapes do not fit in that category.

But if the functionality in Fusion 360 works well for you for doing that type of thing I'd recommend using it to do them, you can then import your model into MoI if you want to do other things with it in MoI.

But really organic forms like you show there tend to be difficult in any program because they are warping and changing so much in 3D space and not easily simplified to a 2D design. It means you have to do the work more like a sculptor rather than drawing profile curves. MoI is based heavily on the drawing profile curves method for modeling, and for certain kinds of models it fits very well and for other types of models other types of modeling strategies can be better.

If you do want to get some tips from other people it would likely be helpful if you were to focus your question on one specific model rather than 4 different ones though.

- Michael