They are in between. A thinner material than the usual athletic socks, they are ultra soft and smooth so they don't add bulk to shoes which are already well-fitted. I love that they have a silicone insert on the inside at the heel of the sock so that they don't crawl down into the shoe when you walk.
They should be fine. I wear all types of slip on Sketchers and they never show...especially if the sock color is similar to the shoe color or your skin color. I LOVE these socks! They never show and they never slip off your ankle...just don't put them in the dryer so the elastic doesn't get ruined by the heat.
These do have more coverage than other no show socks I've tried. I can't wear these with my toms or bobs shoes b/c they come up higher than the shoe. But since they come up higher on the top of the foot they don't slip down into the shoe like other brands I've tried.