Hey Liam, not sure if you still need help, but here's a workflow I've developed when 'sending' my model to Twinmotion. First of all, I save a seperate 3d view named "TM Export". This allows you to hide certain layers and apply graphical overrides. You might have certain layers in archicad that you dont need in TM, for example I hide my trees in AC before sync, because otherwise I cant move these trees in TM.
The second part of this method is creating a DIY proxy system. I have a graphical override prepared in AC that when applied, turns certain objects / elements / doors into a purple material. Then after the sync, I use these proxy elements to replace it with better quality objects. This could be for replacing chairs - you don't want the table to look empty on plan in AC, but you want nicer chairs in TM. Or, you want to add animating doors in TM, so you override them before sync. Once you've made the neccessary changes in TM, you just hide the proxy material and you are left with the correct elements. I have only tried this method with using layers for syncing AC with TM, so I cant vouch for the other sync options.
The graphical override works by looking for a specific property that I've created. It is a simple boolean parameter that I've named "Hide on TM Export". If this property of a certain object / element is false, then the graphical override does nothing. If the value is true, then the override changes the material of the element.
Hope this makes sense. If not I'll be happy to do a short video about it.
AC26 ARM //
MBP M2 Max //
Ryzen 2700x | GTX 1660ti //
UE5.1 | Twinmotion | Corona | Rhino