Question Texture Atlasing and Optimisation

My current workflow involves exporting from Blender to Substance and then to Unity. However, when doing this I'm forced to create an awful lot of materials. How bad is this for performance? Perhaps an even more pressing issue is the size of my project and, ultimately, how big the final build will be.

Is there a way to merge the textures in substance painter into a texture atlas? Am I overthinking this? How bad is it for a room like this to require, for example, 20 materials? The final game will have, I'd estimate, up to 30-40 scenes like this.

 

Best place to start for performance questions is always Window -> Analysis -> Profiler.

 

Thanks. As a general rule, is not using texture atlases bad practice?

 

Can anyone help?