Every friend is different. Here's my own experience on the topic...
My best friend is female. We pal around a lot and are both "touchers" (probably to outsiders we look like a married couple), but sexual stuff is off limits. It implies something that isn't there and, in an opposite sex friendship, you have to have some pretty rigid boundaries. It works for us because we both recognize those boundaries and would not cross them because the friendship is too valuable.
Your milage may vary!