@lowwall is spot on, do not worry about having enough lift. Anything around 20 lbs is fine for warm water rec dives, regardless of gear configuration or conditions. For cold water, 30 lb or so is recommended. I dive primarily in cold water (48F - 58F or so), in an 8mm wetsuit for awhile, now in a drysuit. My first backplate and wing is still my only one, it's a 32 lb OMS Mono. I'll happily dive it until it falls apart. Dove it in warm water and it was just fine, but a smaller wing would have been ideal. If I ever start doing lots of warm water diving, I'll pick up a smaller wing.
I'd recommend a stainless plate, it's only a few extra pounds in the checked back when traveling. They typically provide about 5 or 6 pounds of ballast, spread evenly across your back. Which is just about the best place for it to be, both for carrying on land and trimming out in the water. There are some special cases where an aluminum or specialty plastic plates are preferable, but they are not so common.
Don't stress too much about which brand of backplate, wing, or harness to go for. They're all very similar, practically to the point of being interchangeable. Whichever one you go with, you'll probably be happy for a long time. Can't go wrong with a stainless plate, +/- 20 lb wing, and any harness with a crotch strap.
I do agree that the rubber belts from MAKO are fantastic, much better than plastic. If you haven't tried one, I highly recommend it. Some people just don't like belts very much, so trim pockets are another good way to go. With a steel plate, you're only gonna need like 4-6 lbs of lead or so, which would fit in a pair of pockets. Belts, pockets, and lead are all cheap though (like $30), so you can just pick one for now, and later play around with it to see which config works better for you.
Lastly, I'm surprised that nobody has mentioned this so far. For 2nd stage regulators, a lot of people like to go for one fancy reg as a primary and one El Cheapo reg as a secondary, figuring that the secondary doesn't see much use anyway. Don't do that. Whether you prefer a primary donate or octo donate, get 2 decent regs. In a reg failure or out-of-gas scenario, you don't want yourself or your buddy to be dealing with a s****y reg. Also, you'll always want to bring a reg parts kits in your travel kit, so it's real nice having them be identical. You're already looking at Deep6 regs, which is what I went with, and I'm very happy with them. Also happy with their support.
Edit: oh, and you mentioned on page 1 that you were looking at either a Perdix AI or a Peregrine or a cheaper computer. I would not recommend a Perdix or Teric right away. $200 computers are fine for what they are, a lot of people start with them, and they are mostly pretty happy. If you can swing it, the Peregrine looks SWEET. If I were in the market for a rec computer right now, I'd definitely buy it. It will be a long (L O N G) time before you're ready for the extra features that tech computers like the Perdix offer -- put that extra $600 toward other gear, or toward just getting out there diving.
Add a 3mm suit and you need another 4 or 5 pounds of lift, so a 10 pound wing if there were such a thing. 5mm takes you around 14# and 7mm around 18#. Change to an HP120 and you need to add 3# to all these numbers. I'd add another 2-4 pounds of lift as a buffer in case your weight is not spot on or so you can safely add a hooded vest or go to the next thicker suit.
