I’m currently working on a game with character customization. Some of the clothing options would be better if they’re just another texture on top of the base texture. Is that possible, or do I need to render the combined textures together firstly?
I am not confident that you can do this as you described without baking the combined texture yourself first. What you can do in addition to using a texture is also change a number of properties, in addition to albedo color when you have an albedo texture.
I have an old scene / tool, no longer in dev, which I allow this. Click on a material, and change properties. This may not address your current issue, but you should at least know about it.
I think Babylon.js Node Material Editor (babylonjs.com) could be a great tool to create a material that combines/overlays the textures in a nice manner