you can try to export as twinmotionfbx and when importing into same file (make a copy first) it should ask you if you like to use the scene materials or imported materials. Choose scene materials. I have not tried this myself but it could work. If it works you can easy update the fbx again and again if needed.
The best way is to use our plugin currently in preview and either use the direct-link workflow or importing the content from a udatasmith file.
Here is the link to the datasmith plugin:
Example workflow with using Revit but the plugin works the same in Archicad:
The materials needs to be assigned something in Archicad then you can adjust and improve the quality in Twinmotion or replace them in Twinmotion as needed.
The changes in Twinmotion will not go back to Archicad so if you change the material in Twinmotion than need to match the material in Archicad, this will have to manually be done in Archicad. I recommend saving those different material you create in Twinmotion in your user library folder so you can apply them quickly when updating the model.