The thinner the shirt, the more it wrinkles from personal experience. Avoid broadcloth or poplin unless you want to walk around with the wrinkliest shirt at the office. I've found that twill shirts tend to wrinkle less (fine twill will still wrinkle hard), but the royal twill is OK in terms of wrinkling because its thick. My biggest gripe is that you absolutely NEED to iron the shirts after washing. Steaming won't do the trick (using the non-handheld steamer from Costco). It wrinkles so bad where I wear Charles Tyrwhitt more than S&M with my suits on a day-to-day basis because I'd rather have minimal wrinkles than a nicer shirt on. However, for any formal events, I'd definitely iron and starch my S&M dress shirts since they look and feel 10x better than the shirts in the same price range.
I'd like to say that I have S&M shirts and tried other brands such as banana republic, brooks brothers, and charles tyrwhitt. I have been recommending S&M to everyone for their suits, but its just so damn hard to recommend them for their shirts due to the wrinkling issue. I'm giving their easy-iron shirt a try once they ship it to me. One last thing i'd like to note is that their shirts are without a doubt the best in their respective price range.
- Collars are thick and stay in place without being floppy due to the fact that they are fused
- Shirt fabric weight is relatively the same as the shirt placket and yoke (split yoke too). Have you noticed some shirts such as Banana Republic and Charles Tyrwhitt, especially white shirts, look more white on the yoke (shoulder/back) and placket (button area) than the rest of the shirt? It's because they're cutting costs by using less fabric/thinner weave.