Thanks everybody for their suggestions, so if I got it correctly, harness and BP are basically all the same (and it makes sense since it's just nylon and steel) and the wing is the important thing, in this regard, there are any brands to avoid/aim for? Thanks!
When I first switched to BP/W, I bought my wing from one guy, my backplate from a second guy and my harness on sale. There are videos on YouTube showing you how to thread the harness onto the backplate (e.g.
).
Different plates will have different weights. I dive in cold water with a drysuit; drysuit requires a lot of weight to sink it. I have a 10 pound steel plate. When I go on holiday to warmer waters I have a 2 pound aluminum plate. There will also be slight differences in the extra holes cut on a back plate. But that is more personal preference. When you are first getting started, if you are like me, it doesn't really matter.
The wing is what really made a difference for me. The first BP/W I was diving single tank. The wing was old and had no built in stabilizers. So I had to use a single tank adaptor (STA). So I had the 10 pound plate, 2 pound STA and steel tank. Meant I didn't have to wear as much lead. However for warm water, the wetsuit wasn't very buoyant. So all the gear weighed too much. Switch to a wing with built in stabilizers. No need for a STA. The tank was closer to my back because no STA. Now a 2 pound plate, no STA and aluminum tank were fine for a 2mm wetsuit.
Some wings will have U shape. Some will be donut. Some will have bungee cords on the inside. Some will have bungee cords on the outside. most will have no bungee cords. I like the donut shaped wing because the air doesn't get stuck at the ends. Water pressure will compress the wing, so you really don't need the bungees. But bungees on the outside can get caught on something.
You want the wing to have enough lift so your gear will float with the wing inflated. If I used a 17 pound wing with 10 pound plate, 2 pound STA, harness, steel rings, steel tank and all metal regulators, it would sink; even if fully inflated a 17 pound wing cannot float all my gear. So I have a 32 pound wing. If I was diving doubles, I need more lift. Too much lift and the wing will have drag in the water. So you want as small a wing as possible but not so small it won't float your gear.