... but had opportunity to get drum smoker. It is touted (by the builder) as a reverse offset but it is not a true one as I understand reverse offset-the firebox is in the cooking chamber but the baffle plate covers only the firebox and is adjustable, plus the chimney is at the opposite end instead of the same end as the firebox for a true reverse offset. I've looked at a number of YT videos on reverse and normal offset and most say the smoke from the chimney (for both kinds of offset) should be nearly invisible or blue, that a lot of white smoke indicates a poor fire and will result in bad tasting BBQ. This would be counter to my limited experience with this smoker (haven't been able to produce that clear/blue smoke) and with the WSM. Wonder what the experts out there would say. Thanks.
I don't understand what you mean by a drum smoker being touted as any kind of offset smoker. A drum is vertical. An offset is horizontal.
A drum is similar to the WSM - but the WSM is usually referred to as a water smoker or a bullet smoker.
A drum has a flat top, no doors, pretty thick steel, and usually doesn't include a water pan.
A water/bullet has a rounded top, a side door, relatively thin steel (like a kettle), and includes a water pan. Re water/bullets, the 18" WSM is the best in its class, as far as I know.
I definitely would not replace a bullet or drum or pellet smoker with an offset because an offset is much more difficult to cook with, even if it gives superior flavor. I would get an offset
in addition to a bullet or drum or pellet. Because there will be days when it's too cold or too windy or you just don't have the time to mess with an offset. A nice heavy drum you can smoke/cook with all winter long.
Re the white smoke thing, as mentioned above, white smoke is not bad, it's just not best. But light blue or invisible smoke requires a yellow flame which is very hard to achieve in a drum/bullet/kettle while cooking low and slow. But that stable gentle yellow flame is what makes an offset superior to the other smokers.
I personally don't think a reverse offset is all that. None of the expert pitmasters that I know of in Texas use a reverse offset. You're gonna end up burning a lot more wood with a reverse offset. It's just not necessary.
IMO, in a perfect world, regarding smokers, you'd have three smokers. You'd have a nice kettle such as the 22" Weber with perhaps an SnS charcoal basket insert. You'd have a nice drum or the 18" WSM. And you'd have a decent offset, preferably a top-down offset.
All three!
Good luck.