Best Optic for shotgun?
NONE
i know the bead is the best for some but I have issues with shooting either too high or low.
As others have suggested, I would second more practice. And speaking of practice, slow down, ie. don't try for speed at first, until you've mastered your sight picture (yes, even bead sights have a proper sight picture) and consistent mounting of the shotgun. Only then, once you've mastered your sight picture/mounting.
Experiment with your sight picture - ie. fire a few rounds with your whole bead resting on top of your receiver, and see where that impacts your target at your desired range. If that doesn't work, try holding more/less bead incrementally over or under the top surface of the receiver to see what works for you and your particular shotgun.
I wouldn't bother with ghost rings either - they were originally conceived/brought out as a way to turn the shotgun into a quasi-carbine before carbines "were cool" in either a LE or HD situation, ie. to improve the shotgun's performance at distance. IMHO after much practice and many courses under the belt, I find that a ghost ring actually slows one down significantly at close distances, ie. muzzle to 15 yards or so (the whole reason for being of a shotgun) there-bye giving it more disadvantages than advantages. A set of rifle sights on a shotgun are much quicker close up as you're essentially looking over the sights, and you don't have a ghost ring and base "getting in the way" up close. Even worse are the versions with wings.
If you absolutely have to have a ghost ring on your shotgun, I'd recommend either machining or filing the top half off of the rear aperture there-bye turning it into what shotgun guru Rob Haught terms the "Friendly Ghost" - with that you approach bead sight speed, and still have a good reference for slug shooting at distance. Like this:
The Friendly Ghost is a good compromise, but it's still not anywhere as fast as a bead sight up close, and really does nothing that a standard set of rifle sights won't do, and the latter will be faster up close too. I've recently decided to get rid of my ghost ring sighted 870P's and go back to a tritium XS Big Dot bead for my dedicated HD shotty, and plain-Jane rifle sights for everything else - that way is also far more versatile for a shotgun as well, because if you want to go bird hunting, you just swap on a bird barrel - with your ghost ring sights, if you want to do that, you have to first take off the ghost ring and base, making it a real pain in the a$$.
If after all that you still have to have a red dot sight, I'd recommend an Aimpoint H1 - I tried one for about a year on a tactical shotgun, but ended up taking it off. While it was better at 50-150 meters, it was worse in every way than the issues with ghost ring sights in close as noted above - so much so in fact, that I would not EVER have a red dot sight on a shotgun (unless I was afflicted by some strange eye disorder that made it necessary, or something like that).