No experience with the Gesshin blades though hope to rectify that at some point. I do have experience with the Fujiyama series, albeit not in B#2. That said, from what I've been able to gather about knife making in Sakai, it wouldn't shock me at all if there was crossover between smiths/sharpeners/polishers between the two brands. Indeed, smiths like Shiraki have forged Honyaki blades for both Hide and Konosuke in B#2.
I would caution that with the Kagekiyo knives, you will be paying a hefty premium for the handle. My guess would be ~$150-200 over a Ho equivalent and maybe $50-100 over an ebony equivalent.
In terms of the Fujiyama series, I own a W#2 Honyaki and a W#1 damascus, both 240mm gyutos. The Honyaki is a very recent purchase and ordered the knife with a loose handle install so haven't put it through the paces. The W#1 Damascus has a different geometry and constitution from the typical W#1 Fujiyama series, but I will say it is absolutely one of the most exceptional knives I own (amongst Shigs, Katos etc.). The fit an finish is absolutely outstanding, the grind is a thing of asymmetric convex perfection, and it gets improbably thin behind the edge. It is weighty enough to inspire confidence and the grind is remarkable at separating dense foods, yet through ingredients like onions, it outperforms lasers (the only knife I own that is better through that product is an Akifusa SRS15).
All that said, one of the highlights of both my Fujiyama knives is the treatment of the respective steels. Simply sublime. Could write another two paragraphs on the steel, but running out of steam. Suffice it to say, I like my Konos.