Nope. The drivetrains are all the same.
Nope. Guess Again.
SR5's came standard w/ the manual transfer case shifter - i.e. 4WD
Limited's came standard (option on SR5) with the "Multi-Mode" 4WD that offers 2WD, AWD, 4-HI, and 4-LO. The AWD is basically a selectable locking center differential that will allow you to drive on the street in AWD. You can still have 2WD as well. It's very versatile.
I think 99-00 Limiteds had the best options. For 1999 and 2000 models:
All limiteds have Multi-Mode 4WD.
Rear Locker was an option and is fairly common on limiteds.
All limiteds have 4.10 gears instead of 3.90 gears like on most of the SR5's.
All limiteds have automatic climate control
In 2001, they did away w/ the locking rear diff and added some stupid VSC stability control crap that you can't easily defeat. Also, on 96-98 and 2001-2002, they are 1" shorter than the 1999 & 2000 models. The coil springs on the 99's and 00's have one extra wrap and made them ride 1" taller. After the ford/firestone fiasco, toyota nixed the extra wrap and the rear locker and added VSC. YUK.