This is a reach but you've all got me intrigued with your approaches to grip. Some if you may know this already but in kenjutsu or kendo (any Japanese swordsmanship with two-hand grip. Iaido, the "way of the draw," typically gets there, but starts with an explosive, simultaneous draw-cut with right hand, usually finished with one or more two-handed "finishing strikes" or when encountering multiple armed opponents), the emphasis is a kind of "squeezing" the sword, something like a wet towel, hands "screwing in" towards each other to say it clumsily, base knuckles of both index fingers lining up more or less along the rear of the tsuka or handle, in line with the mune or rear/spine of the blade. The index fingers extend slightly forward, as if "joining" the blade itself. Unlike a chopping instrument, you cut more with the feeling drawing and extending, something like fly-casting - slicing through the arc. The strength is really in your pinkies through your right and middle, with the indexes quite loose, floating almost. Your power is through the left hand and your guidance is through the right. This is all rough approximation.
Any comparisons with any of the grip approaches you're discussing?