No, I am afraid you are not at an advantage being 16 and trying to get into Cambridge, especially with no AP scores yet. Typically, students are a bit older when they start college in the UK. As in, already at least 18 and sometimes closer to 19.
If the Reddit people are honest or have basic knowledge of highly selective admissions OR UK admissions I hope they gave advice along the same lines as we did. OP sounds like a smart person and it’d be sad if they got stuck in a dead-end due to graduating at 16 without relevant APs or DE credits (especially since 2 years of dual enrollment would make so much more sense).
The Reddit users with that experience did mirror the responses given here. Unfortunately for the OP, she also received contrary advice from current high school students who don’t yet know how much they don’t know. I hope she is able to separate thd wheat from the chaff.
At the end of the day, a 16 year old who doesn’t get into Cambridge gets a do-over. Get a job, take a gap year, apply broadly to US universities next go round. Not tragic. This isn’t a situation where a talented young student won’t get a college education. Lots of people overestimate their chances at getting into X (fill in the blanks). They either pivot midway, or get a string of rejections and try again a year later.