Hi! You can look up guides on making daz morphs, specifically for genesis 2 figures. That's the only way to use your own custom shapes for characters. You don't need to rig anything, it's basically just shape keys (i think the maya equivalent is blend shapes?) over a rigged model.
https://hub.virtamate.com/resources/how-to-use-blender-to-sculpt.2302/
In short, you export an obj of the model from daz, you edit it in your 3d editor of choice, you load it back in daz with a specific utility, and do some procedures there to save it as a daz morph. Then you just copy it to a folder VaM recognizes and it loads it up. The guide obv has it in detail
I don't believe any other daz models will work as characters, nor will any custom rigged characters. There are ways to convert morphs for other daz base characters like genesis 3 or 8 to genesis 2, but I've found the process very hit or miss.
Also, there are ways to import custom props like furniture or other objects (but not characters) through unity. There's guides for that too, it's not too bad, but it requires a specific version of unity.
Oh there's also this guide, for wrapping a custom model to a genesis 2 character so that it can be used as a morph:
https://hub.virtamate.com/resources/porting-blender-models-to-vam-wrap2020-tutorial.3312/