The lines are kind of blurred now since the ABZ now is similar to what AB1 USED to be. Body wood, finishes and fancy top options seem to be the biggest difference between those 2.
AB2 is different neck and body woods, semi hollow.
The Combustion came before the NG2, and are what the NG2 is based on. Pickup locations, preamps and colours are the differences there.
Never played any Dingwalls other than the 2 AB1s I owned. Both brilliant basses. Don't think you can really go wrong with any of them. I'd love another some day...