I assume the shtogun game is somewhat similar regardless of location.
So first you should decide how "involved" you want to be. Basically, how are you going to load the shotgun. Dual load is somewhat intuitive, you only need suitable harness and little bit of practice. Not overly complicated or error prone, compared to loading singles. Quad load requires practice. I'm leaving detachable mags and speed loading tubes for now... (i.e. Open Division)
Now you can look at the shotguns. Of course you need to have enough capacity, either off the shelf or with aftermarket parts. This depends on division.
Next how they are (or are going to be) "opened" for the loading procedure. If you stay with dual load, not so critical. Learning the hand/finger positions you can get by with most shotguns.
Next you're going to decide whether you want optics, if yes how they're attached. No point in crippling otherwise good shotgun with unsuitably mounted optics.
Then there's the fit. Might be different than in game shooting, since you're optimizing for different things. You might be able to get something that can be adjusted up to certain point.
Why loading was first and fitment last? Practical shotgun is not a game of shooting, but "not missing" and loading...
