For a lightweight build, you can save a lot of weight by going with a single drive. A single 6374 or larger with a VESC 6 or equiv can climb pretty much any hill and still do 30mph+
For a single drive on urethanes, figure about 20wh/mi easy riding, 30wh/mi hard riding for range, 50-60A max battery amps (peak), and then size the pack based on how far you want to go. 12s2p P42A = 11-20 mile range.