Just to prove a point, buddy at work took to the bush with no camo ... but muted earth tone "normal" clothes, his 1904 Parker SxS 16 ga. bird gun and some 50's vintage
CIL 2-3/4" paper # 5 duckloads his father had hoarded away.
Opening day result: dead gobbler / following day, different spot: dead gobbler, both at about 35 yards.
If you keep your shots at 40 yards or under, Remington's standard Full choke will work just fine, and the Modified choke that came in your 870 Exp. is more than adequate at 30-35 yards. From the past 3 weigh station check points around here ( now discontinued) about 40 percent of the birds were taken opening day and the balanced trailed off more rapidly as the season progressed. Over 50 percent of the successful shooters chose size 4's.
Don't need all the special tricks ... but you do need to sit still and be able to put your pattern on the bird.