Actually I would recommend a combination of different sized containers rather than just one type. This gives you more flexibility to allow for any need to rapidly changing situations.
A 30 Gallon is good for single storage at a fixed location. You can add more to increase capacity of the entire system. Yes at 250 plus pounds each.
5 or 2 gallon containers would work well if you have to evacuate using a vehicle at 38 to 15 pounds apiece. But quickly moved.
But if you have to grab and go on foot The 2 liter bottles are best Each person can grab 1 or 2. Much more and you won't carry it very far.