What is the size of each cube? Starting smaller might help in a new project, but by a modest fraction, not at 1/100th of before.
Do not use the base (default) material for cubes or floor. If using the simple one, add scalar parameters to Metallic, Specular, Roughness, Emissive, Normal, and Ambient Occlusion. Being able to modify those properties on-the-fly could help correct lighting / shadowing artifacts or problems. So, if it’s an ambient occlusion texture, then multiply it by a scalar parameter and convert the texture sample into a parameter (enables changing of the texture used, and intensity of the effect when plugged into ambient occlusion pin). I’d advise only using a texture for ambient occlusion, normal, and perhaps roughness if there’s a different surface type than the regular, smooth one in the mobile game.