Hello Again

So I am planning to wear button down shirts this summer. I have not really worn button downs for years except for dipping my toe in this trend last summer. What I want to know is should I wear my button down with say a denim jacket that also has a collar what do you do with the inside shirt collar? Do you layer it over the jacket? I find that look a bit old-fashioned but maybe it is trendy again with the 70s revival. I find if I just leave it under it looks a bit frumpled and messy. Also do you pop your collars? So in a nutshell if you do wear double collars please tell me how. Thanks!!