Welcome to BYC. Some breeds silkies as an example are reluctant to roost. Others eventually learn how to. Straw is fine as a bedding and does not, in my experience, harbor mites any more than any other bedding.
I have 6 leghorns and 1 silky. They eat about 50 lbs of food every 2 weeks and they are as fat as can be. The don't really perch and when I let them out of their run to play in the yard, they sit and forage with their beaks. Not sure if I should put them on a diet or what. They eat fresh fruits, vege's, grains, etc.