I have already said that I don't usually wear
knickers with leggings.; the same applies to some of my softer trousers if they don't have a nasty seam.
I'm also not going to pretend to understand modern hi-tech fibers but with leggings if I'm not going to wear anything underneath I have always gone for a high cotton content for comfort, likewise I would not wear
knickers without a cotton gusset (never heard of undies with a Coolmax gusset whatever that is but the name itself sounds expensive which isn't quite what leggings or
knickers for that matter are really about).
Around the house, I wear them with shortish tops but going out, always wear a top that drops below my bum!