Voltage is your friend. The motor won't necessarily run cooler, but the ESC and batteries will definitely thank you. You can get away with lighter batteries, less mah for same or longer runtime, and lower C rated packs.

Yup, all you need is a 6s 2200 pack for most tracks to run 10 minute mains. If you are racing with nitros and need lightweight setups for 15 minute mains, higher voltage is the way to go. If you run a 20 minute main, you definitely will need to run 5s and 6s to do it reliably.

I haven't found a significant difference in how the cars drive as you go up in voltage and down in KV. The bigger difference to me just seems to be what RPM you are targeting with your motor and voltage combination.

30,000 rpm = 30,000 rpm regardless if you do with a 2650 on 3s or a 4s 1900 or 5s 1550. The only difference is the mah you need of your battery to get the same runtime across setups.

3s 8000 = 4s 5000 = 6s 3000 generally speaking for run time.