I see a lot of shooters that take a lot of long shots and wound and lose a lot of birds with the 10 and 3 1/2" 12 gauge shells. I firmly believe that most hunters have no business shooting at healthy birds past 40 yards, regardless of gauge, shell length or shot loaded. Closer birds are easier to hit and even more important easier to hit on the front edge. I am not saying that the 10's and long 12's contribute to more wounded birds or are ineffective far from it, just that most people stretch themselves far beyond their limits.
I kill a few geese every year with my 20 gauge shooting regular old steel and a 2 3/4" 12 gives much more effective patterns with goose suitable shot sizes.
To answer your question regarding effective goose loads for 2 3/4" 12, I personally really like 1 1/8 of 1's or BB's at around 1400-1450fps. I am not too picky about brand as long as they give an even pattern at 30-40 yards.