My personal gun / and the gun I think has the most adjustability - and a good all around gun for Skeet, Sporting Clays and bird hunting - is an Over Under, 30" barrels, with a parallel comb ( parallel to the rib ) and an adj comb insert. You can adjust the point of impact on a parallel comb gun / and if you shoot in a T shirt in the summer / double coats in the winter - as the thickness of clothing makes you move up or back on the comb ( where your face meets the comb ) on a parallel comb - the point of impact on a gun doesn't change. On an "angled comb" the point of impact may change 3 or 4 feet up or down at 30 yards ...which is not good.
For me that all around gun is a Browning Citori, XS Skeet model, 30" barrels, around 8 1/2 lbs. 12ga is the most versatile / but 20ga and even 28ga and .410's are availalble.
Some guns - like semi-autos have shims between receiver and stock / so you can change the angle / use adjustable stick on comb pads, etc .....or go to a parallel comb gun.
In terms of just a Trap gun - I go to a heavier gun, 10lbs, and longer barrels 32" - because there is less barrel movement left to right in Trap / and a heavier gun reduces recoil / swings and follows thru better. So for Trap - I like a Browning Citori XT Trap ......but if I could only have 1 gun to do everything it would be the XS Skeet 12ga.
Another semi-auto with some adjustability is the Benelli Super Sport / synthetic stock, comfort tech recoil supression system in it, 30" barrel ... It has shims between receiver and stock / and changeable inserts in comb and butt pad. So you can change height of comb / length of pull ... I use the Super Sport as my bad weather gun / travel gun .... and I like it a lot for general shooting. If I travel, I don't want to take 4 or 5 guns / so I just take the Benelli - its ok for Trap, good for Skeet and Sporting and good in the field for doves, quail, etc ....does everything pretty well. The Benelli is an Inertia gun / not gas operated ...so it shoots a lot cleaner.
I think Beretta makes a decent gun / 391 series, the new series, etc ...but there are other gas guns on the market too ( Browning, etc ). Most all the big names in guns these days / especially Beretta and Browning are giving you a lot of gun for the money.
You didn't say what your budget was ??