I can run my double pan GF with a HeaterMeter down to 175 F or so on natural lump charcoal. I haven't tried any lower since I put a larger fan & damper assembly on it. I suspect it'd work pretty well, seeing how well it holds 175 now.
As far as flavoring wood ratios go.... that's going to depend on how heavily you want the flavoring smoke to be. I burn about 1.25 to 1.5 lbs/ hr, if you want a couple of fist sized lumps per hour, there's where I'd be loading it. I've been using oak natural lump, and have been pretty happy with the results. Hickory lump also works well, I haven't tried mesquite yet (but I should.)
"Measure with micrometer, mark with chalk, cut with fireaxe." Ted M., USCG (ret)
"Smoked pork. It belongs in me." Giles L