I pack way too light to consider using 4 panniers these days, but I have done a wise range of packing styles over the years.

I started out packing fairly heavy (45-55 pounds). At that time I used 4 panniers. The back were kind of medium sized and the front pretty small. I put light but bulky stuff in the back and heavy, but small stuff in the front,

Next as the load got lighter (22 pounds) I went with only front panniers with a the tent on the rear rack.

When I went ultralight (less than 15 pounds) I stopped using panniers altogether and started using waterproof stuff sacks on top of the rack with either a bar roll or a handlebar bag.

I also packed for an off road tour with only very small rear panniers.