1) What is a sensor wire? - wire from motor to esc to make it a "sensored" set-up.
2) What is a puck system? - MIP puck system is replacement rear axles and diff parts that are lighter than stock parts. Good for 17.5 motor racing, we are waiting for release on B5.
3) What is the difference between a “shorty” and other pack types? Shorty is smaller pack, lighter and usually a lower mAh rating. Good for weight savings, B5m only fits shorty or square pack.
4) Never raced a brushless, so is it a good idea to pick up a brushless “system” (motor and ESC combo)? Or should they be purchased separately? I see some of the big names from back in the day are still around (Novak, Tekin, Reedy, etc…) - What you feel comfortable with but yes on brushless, I have done both put I currently run Reedy motors and LRP ESC's, everybody likes what they like and get use too.
5) I have an older Airtronics MX3 radio system (receiver, servos, etc…)… will this work with a brushless setup in the B5m? I’d rather not have to purchase a new radio right now.- Don't know on this.
You will like B5M, good car.