Hi OP, and congrats on the wee one! I have a wee 9 month old (called George 
).
One thing I'll say about the clothes issue - in the newborn fug I was forever worrying about him being too hot cold. He had a hospital appointment at 3 weeks and though it was mid-October and cold I got it into my head that he'd overheat in a sleeps it so took him to hospital in a short legged and short sleeved onesie. Before leaving the house I freaked out that he might be a bit chilly so put a wee sports jacket type thing over it. And suede pram shoes. He looked like a tiny football coach and though I can laugh now, I had zero idea what I was doing.
It is absolutely brilliant and right that you want to help ease the burden on your wife. As others say, respecting her as the baby's mum and therefore the one who knows your DD best is really important, as is telling her what a good job she's doing. Cooking, cleaning, making sure your wife has all the food/drink/cushions she needs for all those hours spent feeding are so helpful. Changing the wee one, dressing her, all the things that aren't breastfeeding.
If you do think your wife is doing something wrong (and we can all do things a bit skew-whiff occasionally in the early months because we're knackered and it's all new), just be gentle and kind about it. Ask her, do you think DD might be too warm in that outfit, as I'm roasting myself? But when you do, keep emphasising what a great job she's doing, as we don't hear that often enough. Respect that she is the one on 24 hour duty. I need to remind DH of that sometimes, that I know DS best because I am with him 24 hours (literally - we co-sleep), and that I respond to questions and suggestions phrased tactfully better than criticism!
If you do want to suggest you help with feeding, wait until DD is 6 weeks and ask your wife if she'd consider expressing so she could get more sleep, as by then her supply should be better established. And if she says no, leave it there.