You're right that "easy to handle" is actually a pretty big concern for rockets, which is why we're moving away from hydrogen and more towards methane.
Methane doesn't require anywhere near as cold of a temperature as hydrogen, meaning that a lot of concerns about things like freezing the oxygen goes away, such that while theoretically a hydrogen engine would have more energy and thus thrust by mass, in practical terms, methane often beats it because the rocket itself can be simpler and lighter.
As far as N6 goes, the trick with this would be that it is a "monopropellant", IE you only need to pump one tank to a thruster to fire it. With hydrogen, methane, or kerosene, you need to pump an oxidizer there as well. So the engine can be drastically simplified because you only need one intake.
However, with energy density there's the critical difference between a monopropellant (a TNT powered rocket engine would technically be a monopropellant, because it carries its own oxidizer), and rocket fuels like methane and kerosene, in that for a rocket, you need to add the mass of the oxygen back in. For RP-1, for example, that's around 2.2 (they usually run a bit fuel rich over stochiometric* because it improves thrust). Yes, it turns out that most rockets carry more LOX by mass than fuel.
For those interested, actual figures:
TNT: 4 MJ/kg
N6: ~8 MJ/kg per the article.
Methane: 55 MJ/kg (15 MJ/kg including oxidizer, ratio of ~2.7 to 1)
Hydrogen: 144 MJ/kg (21-24 MJ/kg, ratio of 5-6)
RP-1/Kerosene: 35 MJ/kg (10.9 MJ/kg, ratio of 2.2)
(Oxidizer ratios pulled from actual rockets)
Given the number of practical rockets (for example, Falcon) using RP-1, 8 MJ/kg for a monopropellant that only puts out N2 would be very interesting.
From my reading, low molecular weight in the exhaust is a good thing (but relatively minor factor compared to other stuff). Which might also by why hydrogen rockets are a thing despite the hassle of H2.
N2: 28 g/mol
H2O: 18 g/mol
CO2: 44 g/mol
CH4: 16 g/mol (running rich, remember? So it is in the exhaust)
H2: 2 g/mol
RP1: 321 g/mol (which might be a reason to run O2 rich for these rockets)
O2: 32 g/mol
*stochiometric: The ratio to completely combust both chemicals. Running fuel rich means some of the fuel remains unoxidized.