In guarding ATM Technicians for a while (my Sons Security Company) your best weapons is your eyes and mind.
Being wide awake.
Carry a Glock 19, best fighting pistol in the world IMO, an extra G17 magazine, have an other in the car, out of sight, but easy for you to get to, grab and shoot.
At the Bank, back in to your parking spot. Try to carry money on your person, hands free. Do not worry about BGs with vests, if you have time to deploy a pistol, aim for the face, they are not going to shout from 20 yards away.
"Hey come over here to get robbed"
Drive up to the cash deposit, open it, throw the bag in, go home.