For hangers, is it any worse if I have most of my tops hung with a broader shoulder hanger?
I know if hangers are too short it can cause the fabric to stretch and raise up at the points. Most of my tops measure 17.5-18" so would a 21" broad shoulder hanger warp the cloth as bad? (21" x 2" to be exact. Currently using some hangers I got from Ikea)
What do you mean by "tops"? Suit jackets and odd jackets should be hung on broad shouldered hangers. Shirts can be hung on narrow shirt hangers if you like (I prefer them folded). Knitwear should be folded, never hung.
You outfit sounds nice, but I would be worried that others might be wearing suits rather than odd jackets. But then I've never been to an Italian wedding, sadly. Could you double check with the bride or groom or their family?