I have an old Bushnell Trophy 4 reticle on my 500 and I also am using an ATI brand AR style stock on mine, which isn't too bad on the cheekweld despite being very tall over the bore.
I prefer the "eotech" style circle dot reticle for various reasons rather than a single dot. Especially for when shooting buckshot. Small single dots on shotguns don't make sense to me.
The circle dot is fast on target, and I have played around enough with it to know what distance is ideal to keep all of the pellets inside the edge of the reticle and when I'm far enough away and to know when to expect "flyers".
I have no idea how the magpul stock would work though. I think you could drop your cheek over on the stock and kind of "eyeball" it to see where your eye lines up to a natural cheek weld placement. If the peep sight sits high, you wouldn't want to add an optic that is going to be taller than it is obviously. And vice-versa if the peep sight is below your line of sight.
The main reason that I am using an optic was the inability to adjust my bead sights on my 500. And it was printing slugs and buckshot so far off where I was aiming, the electronic optic was my only option to correct that.
Is your gun shooting pretty close to point of aim, or are you just wanting to add it "just because"?