Having performed all but the 575 analogue board hack, I would say the others are minor hacks by comparison.And performing an unsupported hack on a Colour Classic board isn't?
FYI, the stock Colour CLassic board will support stereo sound output if a duplicate set of components are added, namely a second Sony amplifier. I have done this by cannibalizing one of the channels from the 575 board. Wish I had heard of the 575 hack before I did it as it would have solved a whole host of problems.
But I am really curious to know what is happening with the Mac TV board (and yes it was full screen, not sure of the exact HZ though). Is it in essence allowing the CC analogue board to produce the larger resolution somehow within tolerances, or is it inducing the same strain as the VGA mod (or is it the hi-res mod, I forget which)? If the former, then it would be a nice secret to learn for all CC mods.