I also agree that you really need to pattern that gun to see just "exactly" it'll do with a given combo.
I shoot a Remington 20 gauge 870 Express Magnum (youth model) for all my shotgun needs now. I replaced the little factory stock with an adult Speed Fit stock. Now it has the nice shorter barrel for calling, but fits me perfectly.
When I first bought it, I spent another $25 for the super full turkey choke figuring I needed it for predators seeing how that's what all the "books" say

. I never patterned it, and proceded to either miss, wing, or destroy everything I shot at with it for about a week

.
After patterning it, I found out why. At 50yards it literally would print about a 2' circle with any kind of load with #6 or bigger shot! I tried a full choke, and it was similar. The modified choke still printed about an 18" circle with any 3" magnums out to around 35 yards. I settled on an improved cylinder, and now it's perfect in my opinion. At 40 yards with 3" magnum #4's, or #2's it prints about a 30" circle, and at 20 yards, it still doesn't turn a hide to screen wire.
Give that 20 gauge a chance. You'll love it in the long run.