Re: Neck Width/Thickness/Wood
Whatever you do just make sure you get a neck without a truss rod. That metal in the neck is a total tone suck and will rob the guitar of upper harmonic resonance. It's a little known fact that the greatest guitarists have had the truss rods removed from their guitars and the neck filled so that it is solid wood.
No truss? Seriously?
Well, if you do go that avenue, based on both logic and experience, I'd sincerely recommend you keep it to bolt-on, quartersawn maple (3-piece probably best) AND w/maple fretboard... That stuff is SOOO much harder and keeps shape a helluva lot better than other popular materials.
AS to the OP's maple vs. rosewood neck, assuming he means fretboard, it's surprisingly influential to shaping your tone. Maple adds brightness a lot, even in the smallest quantities. Ebony, too. And the more, the brighter. A recent encounter with a very maple-heavy instrument showed that even 8-strings, when built with a spalted maple body, maple neck, and ebony fretboard are LUDICROUSLY bright, just plain old shockingly so...
Concerning neck thickness, I'd be inclined to say it affects tone even more through HOW you play... Or, at the very least, that has a major influence. If the profile's good, really thin necks can really contribute to letting you do some crazy stuff, and the cost in tone, if done right, doesn't seem particularly bad in comparison. Although, if you want a thick-profile fast neck, those exist too. ESP Japan (but not its LTD copies) seems particularly known for very strange neck carves that somehow manage to work real nice... like their Eclipse II's relatively thick & narrow (string spacing/nut wise) neck - which IS like half a baseball bat, just a very child-sized bat at that - manages to still be crazy fast, but contributes to the tone the characteristics you'd expect out of a thick neck.
Some tonal comparisons of neck carves and woods will be based on misconceptions though, with a lot people basing their thoughts on thick&rosewood f/b = Gibson LP, thin&rosewood f/b = 80s Ibanez, and thick&maple f/b = Telecaster... Throwing the bias away, though, for example a (proper blonde, not baked) maple fretboard on an LP really does brighten the tone up A LOT, over a classic rosewood one.
Concerning neck (not fretboard) wood, that's almost always various kinds of maple, with few exceptions... Apparently, truss rod or not, maple is just by far the hardest and most durable of affordable and appropriately suited tonewoods, so unless you want lots of problems and a very close love/hate relationship with your truss rod, maple is the safest, most convenient bet.
If you really wanna figure these things out, your best bet is your own ears, a large store with a good hands-on policy, and its wall of stratocasters. Use the same country (MIM or USA) and try to stick to the same pickups between different models - for control purposes, and try out a bunch of different neck options. Beats listening to us!