Sixline wrasses can be hit or miss aggression-wise. The ones I've had were always peaceful and never bothered any other fish.
You will get no guarantees in this hobby. There is no way any one of us can tell you, "This fish will NEVER pick at your corals" or "This fish will NEVER bully another fish". They are like people -- they are individuals with individual personalities. This goes for the sixlines, firefish, chromis... We can't guarantee that the chromis wil fight. We can't guarantee that they won't. Some are aggressive jerks, others are completely docile.
With compatibility, you will get fish that have reputations for being peaceful that are jerks to other fish out of nowhere.
When you stock your tank, no one hands the fish a list of rules that they have to sign off on and abide by. They can be unpredictable and every one will act differently from each other.
What I'm saying is I think you are way overthinking this whole process. Relax, get the fish that you want, judge compatibility based on their "general" and "overall" temperaments, and don't expect every fish to fall into a specific category personality-wise. You will have to take risks in this hobby no matter what. There is no "risk-free" fish addition because you cannot predict their behaviors 100% of the time. So I'd stop worrying so much about needing a guaranteed successful stocking list and just accept that any fish you add will have pros and cons and may not get along with everyone, but there's no way to avoid that. :)