The relationship I have with my spouse would probably fall under the description of "best friends + physical intimacy" though I wouldn't frame it that way if I was starting from how I think about relationships.
One thing that makes it different is that my spouse and I are way more entangled, in terms of what we do every day and what we decide about our future. One of my best friends has moved to 3 different cities in the last several years, and we kept in touch by phone.