Depends on the barrel length.
I've had good success with a Jelly Head .660 with Mag Blend out of a 23" 870SM.
While a Jelly Head .665 patterns better in a 26" 870SM when shooting Mag Blend.
I think generally you'll find a shorter barrel will pattern tigher with a slightly tighter choke diameter when shooting the same load vs a longer barrel.
If I had to pick just one choke constriction for a 12ga Remington , I'd start with a .665 in almost any choke tube.
But, you have to shoot your gun with a choke/shell combo, what works in mine may not work in yours.
I'd also encourage you to look up "deep cleaning" your barrel on the site "All About Shooting". Clark Bush shoots more in a week than most of us will in years.Cleaning your barrel as he describes will make a major difference in your patterns.
Good Luck!