Yes, if you have a custom texture like a normal map or something else that depends on its own UV channel, you can add it to the Atlasflow material and still be able to use the addon normally without affecting these textures.

There are two different textures. A color atlas used for PBR properties that rely on color values and a gray atlas composed of green and blue channels for PBR properties that rely on number values. Both textures resolutions are 128x128 pixel. The color atlas weights 15kb while the gray atlas weights only 629 bytes. The amount of textures used per material depends on the amount of PBR properties being used, ranging from 1 to a maximum of 4 textures per material. In any case, the added weight is minimal.