I won't disagree that an IC and #6 or #4 steel would be a good general recommendation for wood ducks.
But, selecting a choke is really a distance dependant proposition. For shots inside of 30 yards a Skeet choke is hard to beat, if you need a little more range then an IC may be best, and if your shots get out around 40-45 yards then a LM or M may be what you need. You really need to shoot a few patterns in order to know what your choke/load combo is doing at the distance you shoot your birds.
Shot size selection is similar, the farther away the bird gets the larger the pellet needs to be in order to maintain ample penetating energy. The #6 steel pellet would be fine for wood ducks out to about 35 yards but I would just go with the #4 steel pellet since it will handle that duty and provide a little extra range if needed. And in the process, not put as many pellets in the meat which can make eating beneficial to your dentist.
You should have no problem getting a 1 or 1 1/8 oz load of #4 steel to maintain good pattern density if you will try some different chokes.
Here are some pattern numbers from my 12-gauge Browning Citori w/ 28" Invector-plus barrels using Briley flush chokes to give you an idea of what you might get but remember that you need to pattern your choke/load to make sure they are up to par for wood duck killin' (patterns average of five, 30" post-shot scribed circle, yardage taped muzzle to target, and in-shell pellet count average of five).
Sportsman Steel 2 3/4" 1 1/8 oz #4 steel (218 pellets) -- SK / 176 (81%)
Sportsman Steel 2 3/4" 1 1/8 oz #4 steel (218 pellets) -- IC / 202 (93%)
As you can see, the Skeet choke is all I need at 30 yards. This load of #4 steel has more than enough pellets for good wood duck pattern density.
Sportsman Steel 2 3/4" 1 1/8 oz #4 steel (218 pellets) -- LM / 150 (69%)
Sportsman Steel 2 3/4" 1 1/8 oz #4 steel (218 pellets) -- M / 159 (73%)
And, at 40 yards even the LM has more than enough pattern density for good wood duck killin', as long as I can put the pattern on the duck!