From my own initial experiences with being caged, when my wife and I first began we had a reasonably deep discussion on the topic and she made it clear that this would be exploration into a lifestyle choice, NOT simply a game and if it was just a role-play game than it would not work for either of us.
With that said, yes it can be kinky fun although it can become something much more. If you are truly interested in doing it, you will go through a few different ones before finding what work best for you. I would highly recommend shaving smooth or better yet being waxed before doing it as I am sure you would prefer to not get your small hairs caught up in the device.
As you noted, there is a lot of device variations on the market, the better ones are custom made and yes do cost more although you do get what you pay for. As to the accessories/options that you mention, such as ‘urethral tube’, ‘scrotum restriction’, ‘insert able anal extensions’, and configurations which are made for the pierced penis.
Does your wife have a regular lover/boyfriend/bull? Would your wife want to be the key-holder or would she defer that to her other man that you both have included within your marriage? During our initial exploration, the wife locked away 1 key, and left 1 key in a breakable plastic sleeve of sorts. You and your wife will figure out over time what will work best for the two of you and during the road for the three of you respectively.
I would agree with you, the though and experience of wearing a device while the wife is being exclusive with a bull/boyfriend/lover is indeed very arousing. On top of that, to be able to be so close to them as they are physically intimate, yet not able to touch yourself does provide a level of mental adjustments.