First, you don't count the hex you're in. So for your Enforcer, the unit in the next hex is at range 1. There are only a few special cases where anything can fire at range 0, which IIRC usually revolve around infantry/BA doing the shooting. So if you're E, and the target is T, and a _ is an intervening hex, then
ET is range 1
E_T is range 2
E_ _ _T is range 4
and so on.
Second, I've usually played with the 'classic' gunnery 4, piloting 5, which is considered Inner Sphere regular pilot. Piloting rarely has as much impact on a game as gunnery, and makes for more hilarious pratfalls when you fail a Piloting role ;) Again, classically 3G/4P would be seen as IS veteran/Clan Regular, 5/6 as IS green (4/5 is Clan green), and so on.
Playing with 4/4 won't make much difference from playing 4/5, but 3/3 will make hits that bit more frequent - which is probably why your friends enjoy it. BT is a somewhat clunkey game, with lots of rolling required to kill an opponent's 'Mech; anything which improves the chance of hitting will speed play up. And if you're playing pickup games, and just wanting to have fun, then roll with whatever feels good. Herb's rule #1 applies: "If it works on your table, with your players, it's good."
Cheers,
W.