I would say that there is more of a chance of you using the bag in a "natural disaster"
sense vs as a "zombie" bag, so the more you can afford to pack into the bag, the better. In 2004, when Florida was hit with all of the hurricanes and we kept losing power for days and days each time, cash was king, because the stores that did open could not run credit or debit cards. People that needed to
buy tarps and generators used cash. Also, no power means no ATM's.
Keep in mind that during a natural disaster, zombie outbreak or economic collapse, prices on goods will sky rocket. There were reports of price gouging during the hurricanes and rumor had it that a bag of ice cost $10, before the red cross and the government stepped in.
Our hurricane plans in Florida consisted of 4 different households. Each group had at least $1000 on hand- $500 in large bills, the rest in smaller bills, just in case. Fortunately, we never had to use it because we had everything we needed.
I say pack away as much as you can comfortably afford. It never hurts to have cash on hand, and if you keep to paper money, it doesnt weigh much. You are doing it the right way with having lots of smaller bills vs having lots of larger bills.
As far as you using a vehicle as a means to travel, definitely invest in fuel containers and fuel. Having cash on hand, and no place to purchase fuel will not do you any good. Figure out the distance you plan on travelling, divide that by the MPG and then triple it. You wont be getting the highway mileage you are used to getting. Plan on spending lots of idle time in your vehicle, extra time and fuel making your own highway because the regular highway will be a parking lot.
Sooner or later, the fuel will run out. Make sure you have plans the the means to travel on foot, carrying everything you need. After a certain time, ANY moving vehicle will be a target, not only to the undead, but also to other survivors. Unless you have the man power and firepower to defend it, plan on leaving the vehicle behind.