Best ways to texture a vehicle and limit draw calls?

Hi all,

I have modelled a truck and I planning to texture in substance painter.

  • I know I can create just one material slot with atlas textures, which would be the most efficient for a game engine.

  • But I would like to have transparent windows, so I will have to have at least two material slots (one for an opacity layer). However, I would like to make this model as detailed as possible, so I am planning to texture the tires separately as well, but this would make another material slot.

  • I am planning to submit to the Unreal marketplace (it’s the first time I have done so). But should I supply both an atlas texture and also a more detailed version with 3 or possibly more different materials?