#1
For a Solid Black Gloss finish, is it better to apply to a maple top or a mahogany top?
Gear

Soon to have Carvin California Carved Top
Fender MIM Strat (Warthog, Spotlight, Condor)
Epiphone Les Paul Custom
VOX Valetronix Combo
Boss ME-50
Alvarez Acoustic
#2
i doubt it would really matter, except you guitar's tone wound sound different
Shred Head
All that theory my guitar teacher tries to drill into my head just gets buried under piles of porn and I never manage to apply any of it
#3
Depends on the airspeed.

Of course it doesnt ****ing matter. Sand the wood, make it smooth (fill if necessary) and then paint away.