By handle, you mean "Inch"?
It's just what the guys call me, based mostly on my last name and backed up by the fact that I'm 5'7", it's pretty rare that there's someone shorter than me kicking around. I've been called Inch since highschool, I don't even tell new people that I meet to call me that, it just becomes the norm for everyone.
If you're talking about callsigns while flying, it's based on your unit. Here at 423 we're all Talon XX, the XX is the last 2 numbers of the tail number that you're flying, ex. Talon 35 means they're flying airframe number 12435, 406 Sqn call signs are Merlin XX. Some units give people specific callsigns, Moose Jaw is an example. My instructor was Bandit 26 regardless of which aircraft we were in. Formation callsigns are a little different, in Bandit we were either Bandit Shooters, Bandit Outlaws, Bandit Blackjacks or Bandit Cowboys. Broken down even further to Cowboy lead, Cowboy 2, etc. All students are given call signs there too, I was Bandit 105 everytime I was solo, 1 since I was on course 030
1 and 05 since I was the 5th person alphabetically.
As for the headset, don't bother, the plugs won't fit anything in the CF anyway, we use the single NATO plug on most headsets/helmets. Plus the only time you'll wear a headset is if you're flying multi, you'll wear a helmet in all helos and jets including the Harvard and also in the Slingsby. You'll be issued the headset/helmet dependant on your airframe, helo you get issued a Gentex flying helmet that you keep until you release or the 10yr expiry is up and you get a new one, it's a little different than the ones the jet guys wear, ours have the mount for NVGs as well as a lack of bayonet lugs for the O2 mask. Zoomie can confirm it, but I think all the multi guys get issued David Clarks. If you're talking about just using it for civvie flying, you can't beat a good DC, they're the best out there, though some of the other companies are getting better. I own a Telex headset that I wear when flying civvie aircraft.
Hope that satisfies your curiosity.
Cheers