Dynamax Eevee (Can Evolve!): Eevee caught from Power Spot Max Battles retains its Dynamax ability when evolved. Evolving it yields a Dynamax Glaceon, Umbreon, Sylveon, etc. Fast Attack type determines its primary Max Move (e.g. Max Hailstorm, Max Starfall, Max Darkness).
Gigantamax Eevee (Cannot Evolve): Eevee with the G-Max factor (large fluffy mane) is locked. It CANNOT evolve into any Eeveelution and is designed strictly for Max Battles using its exclusive G-Max Cuddle.