You're welcome....and a lot of this is personal preference / and the concept of "Fit" on a shotgun, is something most gun shops have no idea about.
In shotguns...your eye is the rear sight...so a gun simply "Fits" when it hits where you look. Unless you have a lot of experience - and know exactly what stock dimensions fit you ...length of pull, drop at comb, drop at heel - or parallel comb....trying guns in a shop is ok / but you won't really know until you take it to your local club and shoot some shells at the pattern board -with a full choke ...to find the point of impact vs where you look - shooting at a 3" dot at 25 yds or so. If the point of impact is high or low....there are some comb pads / or changes in recoil pads that you can do - to make a shotgun "Fit" you. But a parallel comb shotgun - if its in your budget range....will fit 99.9% of the shooters out there..if you have the adjustable comb insert ...to move it up or down and left and right.../ like the adj comb insert that is on a Browning XT or XS Skeet / although they make guns with and without it - I suggest a gun with it for a target gun.
Even in the "field" for live birds...I shoot my primary sporting clays or skeet guns ....so my primary hunting gun for upland birds is a Citori XS Skeet, with 30" barrels ...and I have them in a 12ga, 20ga, 28ga and a .410 ....the 20ga, 28ga and .410 were all built on the 20 ga receiver...( they're all stand alone guns ) .....but there are also systems ( full length sub gague tube sets - sold by Briley and Kolar...) where you can turn a 12ga gun ...into a 28ga gun, etc by inserting this tube set that is fitted to the gun. Don't confuse "full length tube sets" with "screw in changeable choke tubes".
By the way, I would not recommend you buy a shotgun - that does not have changeable screw in chokes - so its more versatile. That way you can use one gun ( with a Mod choke in it for Trap singles, with a Skeet choke in it for Skeet, with maybe an Imp Cyc and a Mod in it for sporting clays). I buy a set of 10 choke tubes for each of my guns ...a pair of Cyclinder, pair of Imp Cyclinder, a pair of Skeet, pair of Mod, one Imp Mod, one Full...( some guns come with 5 chokes, some come with 3, some come with only 1....) and they're about $ 50 each ...so take into account what chokes the gun has if you're buying it used. There are a lot of used guns out there -with fixed chokes still made prior to the mid 1980's or so ...when Browning and others brought this concept to the market.
Watch chamber length too ....remember shot shells are measured after they are fired. A lot of "Trap" guns are chambered in 2 3/4" shells --- you can't shoot a 3" shell in a 2 3/4" chamber ( but a 3" shell will fit into a gun with a 2 3/4" chamber ) but when fired, the folds on the crimp won't have room to open properly significantly increasing the pressure in the barrel - maybe with disastrous consequences.
I was just in a used gun shop this afternoon ...and 2 brothers were looking for a SXS shotgun ..no experience, buying solely on price ...until one guy told them, it has 2 1/2" chambers in that old gun ....can't shoot common 2 3/4" shells in it...or steel shot ....and they had no idea what he was trying to tell them -- so a couple of us helped them look at some guns ...with different chamber lengths, screw in chokes, etc...and I don't know what they bought ...but at least they knew more than just price. The shop was a madhouse...hard to get customer service during this buying frenzy going on right now. As experienced shotgunners - we all need to help out a little when guys are new to this part of the hobby. The owner thanked us for helping out.../we're regulars - coming in looking at whatever somebody might be trading in to add to our ever growing collections ......but sadly no high end revolvers, or 1911's caught my interest...and I have 25 or so shotguns, so I sure as heck don't need any more shotgus....but you have to keep your eyes on these used gun stores...stuff comes in every day ...and you just never know, when something might want to follow you home...