The GV-1 would be the same as the GV-2 for the smaller set of bright lines , and the larger set would not be accurate for the wide conversion lens . "They" say that the brightlines represent about 85% of the actual image . I , for one , would like to think I am good enough at framing to be allowed to use 100% , hence my use of the 24mm finder [ - 85% = 28mm , or there abouts ] .
You still have to take parallax error into account.
Also 85% is a lot more than you think, we're dealing in 2 dimensions so you take the square root of 85 and get 9.2, so in any given dimension it's 9.2 vs 10 (square root of 100) or 92% vertical and 92% horizontal. Which is only 4% from the top, 4% from the bottom, 4% from the left and 4% from the right. (0.92 x 0.92 = .085).
Viewfinders aren't made for perfectly accurate framing (again, parallax error, and the GV-2, being smaller would have less parallax error than the Panasonic, Voigtlander etc. style - those viewfinder being larger & therefore further away from the lens. They're made for rangefinder style photography - action, reportage with zone focusing, not critical framing - if we wanted critical framing we'd own SLRs or only frame using the LCD screen.