If you ask me, Glaceon is best suited for double battles with a high amount of synergy. In this circumstance, Glaceon excels as a hybrid role of attacker and support Pokémon. In my experiences, Glaceon is used almost solely by Japanese players, and the most common moveset is Icy Wind, Protect, Helping Hand, and Freeze-Dry/Ice Beam/Blizzard. Effort Values are 252 HP, 252 Sp. Attack, and an unknown amount in the remaining stats (it's hard to see from the hexagon chart); Nature is Modest or Bold; and the hold item is Bright Powder (if Snow Cloak) or Leftovers (if Ice Body).
Glaceon is most commonly paired with Lapras (for Aurora Veil support via G-Max Resonance), Weavile (very fast Pokémon who can set up Hail and activate Glaceon's Abilities using Max Hailstorm), or Abomasnow (Snow Warning instantly sets up Hail and, again, will activate Glaceon's Abilities). Snow Cloak is preferred over Ice Body. Most of the time, Glaceon and one of the above will show up right at the start of the battle, though sometimes only Glaceon's partner will be there at the start with another Pokémon, and Glaceon fills in later for when one of them is knocked out. Increasingly often recently, Arctozolt will show up late into the match, after Glaceon's Icy Winds have lowered the opposing Pokémon's Speed enough for Bolt Beak to deal extra damage by going ahead of its target.
Something to bear in mind is that Glaceon is strictly for advanced players, ones who already have a keen sense of Pokémon breeding and training as well as a grasp on Pokémon battling trends, and the same goes for teams like the ones I'm describing. A Glaceon-based team MUST remain in control of the match from start to finish, and it requires very good prediction skills, as they contain a lot of Ice-type Pokémon and so opponents will select Pokémon that can deal super-effective damage. You'll need to accurately figure out what they'll bring out during Team Preview and counter accordingly.
I am not certain about this, but I'd advise not to risk it. Pokémon Bank considers different save files as different games, and accordingly, Pokémon brought over for storage from a prior save file can't be deposited into a later save file.