I’ve bi-wired with Audioquest in a number of ways. Of course, they will tell you to bi--wire as symmetrically as possible. However, I’ve had good success with breaking the rules, somewhat. I use a combination of 6ft Mont Blanc (12 AWG, PSC+ copper, counter-spiral geometry) for LF and 7.5 ft KE-4 (15 AWG, PSS silver, star-quad geometry) for HF. Close to 2ft difference, different metals, different geometries. I like this combination a lot. I’ve compared it directly to 8ft Redwood single-biwire ($8500 MSRP) and it was a wash, with some points going to the Redwood and some to my weird biwire.
I ended up preferring full double biwires of Kilimanjaro (PSS silver version of Mont Blanc) or Wildwood (Redwood with more PSS silver), at much greater expense, but the quirky mismatched biwire is still one of my favorite speakers cables, and I still use it in a smaller office system. The combination of PSC+ copper and PSS silver yields a really natural timbre. I didn’t like the Thunderbird Zero (alone, no biwire) at all, so I’d say it’s better than that.
As far as coherence, I’m a guy who dislikes the Tannoy supertweeters because it messes with coherence, but I don’t have any problem with this mis-matched biwire. You’ll be fine!
I also have a single-biwire Rocket 88 in my gear collection, and it’s a really nice cable for the money. Good for helping to smooth out a solid state amp!