Bathroom Exhaust Fan

[Jedi]

I'm remodeling my bathroom and one of the first things I'll be replacing is the exhaust fan. My home is a 1 story home and I have a stair case up to the attic which is just insulation and about 6' tall in the middle. Today I went up there and was surprised to find that I have a double ceiling in the bathroom area. Should I pull the ceiling and add vapor barrier or should I just leave it? Secondly I was going to use a rigid line for my exhaust, should I run it straight up/over/and through or over/up/across and through or should I just buy a flex line?

Thanks