Cool! A 12s3p with P42A or similar cells will 100% get you 20km of range, probably more like 30km.
Are you interested more in crazy torque to get you up hills, or a lightweight, reliable (less moving parts) board? Option 1 means belt drive or gear drive, option 2 means hub motors or direct drive. If you have good roads, hubs FTW.
If you’re on a tight budget, you might be stuck with single drive, in which case a belt drive or gear drive will be needed for good torque. That being said, I really like my single hub-motor board. Need to push with my feet to start / stop, but the cruising and freeroll are fantastic.
I’ll post a build thread of it tomorrow, putting finishing touches on it this evening
Edit: done – Small board | Loaded Coyote | 12s1p | single hub