We took soooo much stuff and i thought we were packing light
In anaheim and nyc and orlando in nov we were fine with just a light weight cardi or hoodie plus regular tshirt and jeans/pants/yoga pants. I would take 1 cardi in black or grey and 1 hoodie in a black or grey. You can get a lot of wear out of mix and match clothes like that..
In may, that should be fine
Re washing most hotels will have laundry facilities and/or laundromat style coin operated facilities. They provide powder and softener etc and it will only cost a few dollars to do a load

i found this easier than having to remember laundry detergent in my bag
Re the hair dryer thing... I used the hotel's drier and i had no issues. If you need something super duper you could always buy from
walmart or walgreens when yimou get there. Take the least amount with you as possible. Also the weather there is different. My hair is normally quite curly and unruly but in the us it was straight and perfect to style
I recommend using packing cubes, take adaptors, take a notebook and pen, take a few ziploc bags for odds and ends and put all toiletries in plastic bags inside your toiletries otherwise you may end up with exploding shampoo which is messy!!!