Q: Do you think that there's a tempo middle ground where you could feel the time signature of a song as being either a "fast 3/4" or a "slow 6/8"?
A: sure. people get 3 (or 6) feels mixed up all the time. one of the hazards of putting out a song with any kind of meter divisible by 3, is that some people are gonna always hear it the wrong way from what you meant. this pretty much doesn't happen with 4, because there's only 1 prime factor i guess is what it boils down to