Decal Best Practice

Hey everyone. I I have a modular city builder in the works and want to use decals for grunge and wallpaintings. Right now I use custom geo for my decal atlases instead of any flipbooks but in the long run I do want to keep it somewhat clean. Would you recommend using decal actors or stick with geometry and a decal shader.
Main concerns are useability with instancing in HDA’s and performance.