5G doesn't have any bearing on the range, the frequency does -- 5G lowband will have about the same range is 4G. But to see the blazing multi gigabit/sec speeds, you'd need the high mmWave frequencies, which does limit the range,
kinda stupid question: (not meaning to sound as an asshole question) Isn't the mmWave part of 5G itself ? Or what would you define as 5G ?
Their standards committees agreed on certain bands of frequencies, some with more capacity than others.
I'm not an RF engineer, but given 5G can operate on frequencies higher and lower than 2.4Ghz, then I don't suppose there's any reason you couldn't if you were hacking up your own transmitters/receivers. A regular phone wouldn't, though, as they don't have 5G radios that can talk on those frequencies (or they've got hardware filters of some kind to ensure that they don't).
Of course, all reports on it will emphasise the new stuff, so it's easy to get that impression.