I wear Leatt Airflex Pro elbow pads under my long sleeve shirt all the time (almost every ride, for the last 6 years), and I don't even notice them. Great piece of kit.
I've not tried to wear jeans while riding, but my 7IDP Sam Hill pads caused chafing on longer rides with long pants. So I tried the Rapha Trail pads, and I've been really happy with those. They're lower profile, and don't chafe/bunch up while wearing my Endura Spray pants.