I've used shotguns all my life. I've shot a lot of different ones as well because on Saturdays sporting clays practice we would all try our friends guns.
We all competed and all shot O/Us. They are the best tracking shout guns - by far! And if the gun doesn't fit you will shoot badly. My brother had a top of the line Beretta sporting gun and we both couldn't shoot it. And then I have a 28GA Beretta Silver pigeon and never miss with that one, off the shelf too.
You can buy any O/U gun that can be fitted for you but some cannot because it's super expensive. That's obviously extra but if you really want to compete and shoot at the top it's the only way to go. There is a really good reason to have an O/U fitted.
I bought a Browning 425 Sporting clays gun and had it fitted. That gained be about 5-shots out of 100. So, I was shooting in A class by then and that upped my scores from 93/100 to 98/100 and I began winning or tying for the win. I was also reloading and shooting a lot. A number of years at the top of my game I reloaded and shot ~25000 shells/year - shooting ~500 shells a week!
That Browning is still with me, built like a tank! and shoots with the best guns in the world at a very reasonable price. The only thing that can and eventually will go wrong with the Browning is the barrel locks. They wear out an the gun opens itself when shot. Replace springs and keep going, or don't let it get to that point. Not expensive either. My Browning 425 is still running on the original springs after probably 75,000 shots (2 barrels so half of that each).
Well maintained as mine is, these Browning O/Us will outlast their owners! Mine below is 33-years old! And yes, it's been refinished. Inevitable, no safe queen this one.
Pictures (2) of that gun below (high res):
This second picture shows the lever that opens the gun for loading. It works like a wear clock for the springs. Right now it's past the center line and to the right. When it was new it was left of the center-line about the same amount. So, it's ready for a springs change!