General note, you do mostly have to have control of the asset pipeline. Most of my demos used paid assets, and almost none of them worked out of the box. I had to import into Blender, fix scaling issues, texture/material, etc. and probably like half of the models were beyond repair. So you want to have a DCC tool of choice, like Blender, and get the pipeline solid first. Sadly many apps use proprietary formats or don't support open standards, which leads to unneccessary compatibility issues. Just the nature of the game.