It seems as though other than materials (stainless steel - SS, Aluminimum - AL, or ABS - plastic) most plates are pretty standard.
I just recently switched myself and found that a SS plate with a SS tank gave me the correct bouyancy, but put all the weight on my back so if I leaned to the side a bit I was being pulled to roll over. A SS plate with an AL tank and a few pounds in the weight belt seemed to be most stable. (really really stable) and I am using an AL plate with a SS tank and find it's not too far off, however the weight is a little farther away from the body, so not quite as ideal.
If you are going to use a HOG harness, that's a one piece webbing, they all work the same. Some brands of webbing seem to be softer or stiffer depending. But there is a pretty standard configuration on how they go together, but there are some variations. (ex. For my wife we added a quick release buckle with 8 inches of webbing under the left chest D-ring but didn't cut the webbing. When unclipped this allows a little extra room to get in and out of which was a concern of hers. I however found I didn't need it.)
As far as wings go there's a few options. First there are single and doubles wings that correspond to your tanks. As a S. FL diver most of us don't dive doubles so we're looking for singles. There are a few wings that claim to do both. This was initially what I was looking for as my though was - Hey some day I might dive doubles. Let me save the cost. This isn't the best idea. It seems that those wings tend to "taco" on a single tank. That's where it wraps around a bit. the trapped has is harder to vent - more drag - you get the idea.
Wings also come in the classic horseshoe shape or doughnuts. The difference here is if the bottom of the wing allows gas to pass from side to side. In a horseshoe it does not. I have a doughnut and I've heard a few people say if they had it to do over they'd go with a doughnut. I tried a horseshoe and found that If I was in a good head down position the gas may trap to one side. In order to move it around to the side with the dump I had to change my trim and lean. I am sure this gets easier as you get used to it, but I'm on the work smarter not harder camp so the doughnut seems like an easier way to do it.
There are some other options like a bungied or non-bungied wing. I can tell you that DIR is strict non-bungie and they give reasons such as entanglement on the external bungies and gas trapping. I have not tried a bungied wing so I can speak of any benifits, but I can see the reasoning on the non-bungied.
Some other things in the construction area are inflator hose length. DIR seems to lean that a little shorter is better. There's the pull dumps - and knob or no knob. Again a ball is seen as a possible entanglement so it is not DIR desirable. And is it a single wall construction or a bladder inside of a shell.
Finding shops that stock the stuff down here seems to be a little tougher. But there are some... I was sold the first time I tried it. The BP/W seems to move with you much more. I noticed my trim got better and I could make much better small adjustments. Instead of trying to find a BC with a good fit, you can make the harness custom fit you.
Hope that helped a little. Good luck!
