Think more in terms of watts rather than voltage - a LR 1.5ohm atty at 3.7 will give you the same kind of wattage (heat) as a 2.8ohm atomizer at 5V or as a 4ohm atomizer at 6V. That's the concept behind the famed Darwin mod, it's a variable power (wattage) device unlike variable voltage devices.
I believe the max wattage most atomizers can handle is 12 watts, and even then that's pipping hot and most
juice will just taste burnt.
As Concat said, it all depends on the
juice. I find that complex flavors (i.e. Boba's Bounty, eJoker) come alive at higher heat, you start noticing all sort of subtle flavors, where are other juices such as fruity juices just taste burnt.