RE: Reducing the surface area of the wings for going faster?
It's a wee bit more complex than all the above.
As long as you are only flying in un-accellerated flight, span doesn't matter all that much. But most of us need to turn the airplane, so induced drag becomes an issue.
Reynolds visits some ugly truths when chord goes away.
Nobody cares about supersonic designs when designing RC models. Might as well talk about spacecraft.
The wing is the small part of the overall drag when flying level. When you turn, it dominates.