Since I'm a 6w7 sx/so and CP on top of that, I usually look for people who were "popular" in an unconventional way at some point (eccentricity or people who conformed in non-conformity or people who had oppositional defiance issues in their youth) ...I think it can be difficult to confuse people like me with 4s, because you'll see a lot of goths, hippies, etc who seem like they're trying to be "individuals" by being covered in tattoos or wearing black lipstick or going on rambling soul quests who are actually CP 6w7 SX because you'll eventually see they actually take a lot of comfort in intensely identifying with that GROUP instead of being completely unique. It's the idea of being a part of the conterphobic or oppositional group, and it's not always political, but yeah you can see this in a lot of political activists who join communities or form cliques around Bernie Sanders, veganism, or in the case of my boyfriend from high school, whom I believe to be a different MBTI type but the same enneagram, he's always been a very "likeable" bad boy, he's covered in tattoos, and he's always in a band, but his identity involves belonging to those groups not being above or elitist or completely unique from others. And he will randomly bust out with some political stuff when you least expect it, and he actually tends to make a great point when he does, because he usually appears to be more interested in things that are creative or social. I could be wrong though, but only slightly, that he's a 7w6 SX/SO which is why he has that escapist veneer constantly (while I'm constantly cynical and concerned but then randomly an escape artist).
Idk. I suspect it a great deal in people who are unconventional but in a diplomatic rather than elitist way, who formed their identity by fighting the good fight, defending the underdog, or being popular among eccentric or unconventional groups (in high school you would think of this as the skaters/punks/artsy kids rather than the preppy kids, in adulthood it could take a political shape, or involve belonging to adult sub-groups like hipsters or rock-a-billies or horror movie people, in which you'll also find a great number of 4s, but they're a little different).
Speaking of horror movies, my ex who I believe was a 3w4 showed his 4 wing by being very elitist about his movies, he'd always created this 4-ish wing by thinking it made him special, unique or more interesting than other people (then when he was depressed saying it made him weird or nerdy)...while for me, horror movies were never a source of elitism, it was more like I belonged with a loose collection of people who understand dark things, it's fun to bond with people about it (in fact it's part of what made me bond with my ex. The shared identity, not the separation) and it's funny how I treasured this thing we SHARED and he would occasionally defensive that he was more of the "expert" and I let him have that, because he worked hard at it, and I didn't really care, because that's not what I formed my unique identity around, it's something I use to bond (6) unconventionally (CP) and escape from reality (w7) because I'm intense and fascinated by sex/death/mental illness/paranormal phenomenon (SX).
I actually freak out when I'm part of a best friendship, or couple and we can't share at least one deep intense sameness. The sameness is important to me, if that sounds weird, idk.
Or with vegans. I think you can tell a 4 vegan by how they're like "this is how I live my life, I don't care if you're not vegan, because I obviously more compassionate and intelligent than you, and aren't the evangelical vegans annoying af?" And I am more like "how can we get more people to be vegan or at least vegetarian to benefit humanity as a whole" and I while I don't think certain methods are effective, I respect evangelical vegans, even when I think they're wrong, it will work on someone. My unique identity isn't wrapped up in being vegan, but my CP tendencies give me the strength to defy cultural norms consistently so that I don't struggle with the social aspect. So with vegans, I look more for people who approach it as I do, who seem very concerned about humanity and have an intense sense of purpose, rather than an elitist attitude about it. And as more people become vegan, the 4s will go raw or something extremely difficult to protect their unique vegan identity.
So sometimes it's hard, especially since my heart fix is 4w3, but that's how I see CP 6w7 SX/SO and separate them from 4s.