Some clarification....
1) A stainless steel plate will help offset the amount of lead needed to sink with a 7mm suit, however depending on how much weight you need, it may make you overweight. The plate itself is 6lb's.
Yes, though I'd be surprised if you were overweight in a 7mm. The other consideration is travel. I have a great SS plate from DSS, but sometimes it just doesn't make the traveling squad, particularly if I'm going someplace warm and don't need the weight. You can always get aluminum and carry more lead if you need it, but if SS overweights you in warm water, you're just stuck with it.
2) Many will argue yes they are all the same, but I say no. There is difference in machining that you may care about, and there are plates that are better in the eyes of the user than others. I had a DGX plate at first, it had burrs that tore up harnesses and the holes didn't align with some aftermarket parts (back pad)
Yes, but most are fine. Failure to align is mostly a result of the fact that many accessories are designed for that mfg's plate. It isn't a quality issue, it's just matching. Getting a high-end plate is no guarantee that the holes will line up if you want to bling it out (not that you should).
3)I prefer a 1-Piece continuous harness. other harnesses out there that drive up the price and are not worth it due to additional failure points like plastic buckles and other "creature comforts" that are unnecessary.
Disagree. There are some people for whom something other than a hogarthian harness is a better solution. I have several, but find that they are not comfortable for me in certain configurations. That's just me and my body type. They are also a bigger hassle in a drysuit. I have two versions of the dive rite harness with transition rings (one even has QDs - gasp). If continuous weave works for you, that's great - cheapest and the most robust. But don't let anyone talk you out of something different if it fits you better. The whole "failure point" thing is overhyped. A sternum clip coming undone or a QD letting go is something you probably wouldn't even notice on a dive, not that it is likely to happen. I've had several classes where standards require that divers with QD buckles on their harnesses demonstrate they can manage a failure. Each time, the instructor has snuck up on me and undone one, I've never even noticed. Eventually, he'll point it out, roll his eyes at how stupid the exercise was, and I'll reclip it. People act like you'll explode or something. Bull.
So, I have no problem with continuous weave and would suggest you try it first because if you like it, you've saved money. But, I wouldn't hesitate to go with an alternative if it makes sense for you. You'll find there's a lot of "orthodoxy" preached about BP/W setups and much of it is a good starting point, but don't treat it like an appendix to the 10 commandments.
4) you can search far and wide on wing lifts and will never get the "best" answer. warm water most use something in the 20lb range. cold water the 30lb range. anything above that and you are looking at something that is not optimized for a single tank and can add drag in the water. Avoid horseshoe and bungee wings. Donut shaped are best.
I agree that bungee wings are best avoided, but "donut is best" is nonsense. Different strokes for different folks. Most divers are rarely head down enough to take advantage of the lower part of the donut. I personally like a horseshoe because it is less likely to get pinched on the bottom (which is the #1 cause of bladder failures) and because I can park a little air on one side or the other to compensate if I have a stage slung on that side or if I want to swim along a wall facing it while taking photos (i.e., cocked to one side). It can be a handy tool. Necessary, absolutely not. Donuts are fine, but they aren't "best" unless they are "best for you."
In terms of lift, there are a million threads on "how much lift do a I need" that will tell you how to figure that out. One of the benefits of a BPW set up is that you can swap out wings when it makes sense if your situation changes.