Sorry to come to with a basic request for help but I have been out of the game for a bit and completely lost when it comes to logos (it used to be a case of upload and its done haha). I have tried using SVG logos as I don’t want to lose quality depending on the device/browser, however I could not get it to render a simple one colour graphic element, so figured a transparent PNG would do, however originally, the sticky nav version was bigger than the header version and it want it to be smaller in the sticky nav. I created a smaller version hoping that would shrink it but the theme is stretching it when you it brings up the sticky nav version and I cannot for the life of me work out why.
i would suggest you use your original good quality logo for sticky navigation and mobile header.
In Customizer > Layout > Sticky Nav – you have an option to adjust the menu item height – reduce this slightly to also reduce the sticky logo size.