When you’re newer, you want to save sexualization for isolation, yes.
When you’re more advanced and you have an established sexual vibe, you can be sexual in front of a girl’s friends and have them approve, but you have to already be the sort of guy a girl’s friends will say, “You should TOTALLY hook up with him,” about. If you’re not that guy yet, it will backfire.
When a woman’s intrigued about a man, this generally leads to sexual tension, yes. The two emotions seem to be linked. Even if he’s not a guy she’d usually be attracted to, if she starts getting intrigued, she’ll start getting attracted. And fractionation does indeed generate intrigue (and thus, attraction)! You’ve got it. Fractionation = intrigue, which in turn = attraction. That’s basically how it works.