Lump has zero fillers, so it will burn cleaner yes, which means less ash.
Personally I only use lump when I'm grilling, I use briquettes when I'm smoking, unless it's in my COS then it's wood splits.
Biggest thing is making sure whatever you're putting in has a chance to 'preheat' in whatever fashion you choose, either lighting it up in a charcoal chimney, putting them to the far side of the lit coals allowing them to heat up from radiance before being ignited. Basically the longer it takes to fully ignite the more it'll smolder and the longer your meat is exposed to 'bad smoke.'
The Life of the Knife is Ended By! The Wife.