Re: Middle and Bridge pickups
Position 4 will work better for clean tones. If you think of classic U2 songs, that's all position 4 on a Strat.
You can make any pickup sound darker by rolling off the tone pot.
IMO hard rock and metal are all bridge humbucker - solos included.
Eh, I think you can get a lot of mileage in solos with the neck pickup, especially more fluid parts like legato and tapping. The warmth really helps smooth it out. I actually think tapping tends to sound better on the neck pickup.