Huh, where are there game-breaking glitches in the first two Zelda games, I never ran into one. I know that in aLttP there's that glitch with the mirror where you can go "under" a dungeon and do several other things, but you must really try to get that on purpose. But in the NES games?
Actually there aren't that many differences between the versions.
As far as I know in LoZ only the soundtrack is a bit different (the Famicom version has slightly better music). And in AoL there are some minor differences, here I prefer the NES version. Someone made a video about the differences: