I’ve only been shooting turkey only for about 5-6 years now, but have had great success with a 20 ga Franchi O/U with extra full and full tubes, shooting 3.5” 1 5/8 oz of 6 shot. I limit myself to about 30 yd max and have taken a bird every year I’ve hunted.
I too patterned a 1/2 dozen different loads when I started and found one gave better patterns at 30 yds then the others, I gave my brother who’s property I hunt the extra shells. There is a difference in patterns you don’t notice until you put them on paper.
Having two barrels I also found a difference in what shell each of them preferred, but stuck with just the shell that shot best in the tighter tube.
To be honest I don’t know that all my birds couldn’t have been taken with my old M1200 12 ga with straight mod barrel and think we tend to over think some of this.
Birds will come fairly easily to a call and decoy if you keep still and Hidden, I use a old deer blind. Keep your shots within range and place them well, that’s the trick.
This years bird taken at ~25 yds