For my M12 tools I have more of the 3.0 and 4.0 batteries since I tend to use them in my drill and impacts where they can get used up quickly. I have the 3” grinder and a couple of cut off tools in that size as well. They eat up the small batteries fast.
I have the small batteries for when I need to use it in tight quarters, or when the bigger batteries are charging.
I only have the drill in M18, but am still considering the electric impact. I tend to use air tools still.