First, thank you VERY much for taking the time to explain it. Second, with the choices you list, it is not a good thing. This means that I'll be spending lost of $$ to buy all of the choices as I want to experiment with them all
Not really necessary, just like PC's today it's pretty hard to beat the function and value of a packaged system. It's possible to by a tower and Motherboard etc. but you will spend more, deal with compatibility issues for little or no gain. Frankly until you build a little time you can't really evaluate all the choices.
1. Is the "single tank" adapter that would be available if I bought the "Single Tank" system at the instead of the double tank system at the beginning?
Single tank adapters are just that an
Adapter. DSS and now others offer single tank systems that do not require any adapters.
2. If I bought the "single tank" system at the beginning, would I have to buy some sort of an adapter to switch to the double tank setup in addition to using a different wing?
No, doubles bolt right up to the back plate.
3. Is there a wing that can be used for both?
Classic question. First take a look at *why* divers move to a BP&W in the first place.
Less clutter, easier to achieve horizontal trim, easier to vent while horizontal, less inherent buoyancy etc.
Using a doubles wing or a "dual purpose" wing with singles will reduce or negate many of the advantages of a clean, well designed, properly sized BP&W.
Doubles wings are far wider than singles wings. That is necessary for use with doubles, but it means more drag and more difficult venting when used with a single tank.
In most cases you can use the same plate and harness with singles and doubles, but you need another ($300) wing when moving to doubles.
Now consider the cost of moving to doubles:
2 set of doubles (or more!) tanks, bands, manifolds......$1200-$2000
1 Drysuit and a couple sets of undies............. $2000-$4000
4ish deco stage bottles with rigging .................$800
Can light ............................................................$1200
5-6 regulator sets...............................................$3000
Suit bottle (argon) + reg.......................................$250
Dry gloves, gas, training, reels, spools, spare masks, pee valve, backup lights, 30-40 misc bolt snaps, etc. etc. etc.
The jump to doubles is expensive. $5000-$10000 easy.
Trying to save a few $$ now buy purchasing a dual purpose wing that isn't a good singles wing and is also very possibly the not the wing you need for doubles *either* is simply false economy.
BP&W's can be confusing, and there are lots of possible permutations, I'd be happy to walk you through the choices.
Tobin