I have a GOSM widebody and have found chunks work better than chips. 2-3 chunks is just about right but only last about an hour so you have to keep adding to it. The factory wood pan is fine since you don't really have to overload it.
When I first got mine I couldn't keep the temp below 250* until I did a couple of simple mods. I dumped the water and filled the pan with sand, this will really help maintain more stable temps. I can still place a disposable foil pan on top of it with a little water to catch drippings.
I also installed a needle valve
, this really helped me get lower temps and gave much more control.
I have since made a lot more mods but those two really got the smoker working like it should.