IVs and EVs

Polished has a hybrid game mechanics of the modern and the vanilla for stats.

IVs

The IVs in Polished range from 0 to 15 and are stored for each of the six stats. The flawless IVs would thus be FFFFFF.

• The IVs determines the type of Hidden Power as expected.
• The game has the IVs vary color option among the preferences at the start of a new game. (Oh, this seems to be forgettable. :P)

EVs

The EVs in Polished have a maximum of 252 for each of the six stats and, unlike the modern, have no limits to the total points; i.e. you can max out all the EVs of an individual Pokémon. The maxed out EVs would thus be FC FC FC FC FC FC. Each species has its EV-yield data defined as expected.

EV grinding

Polished has the Power items and, as an exclusive QoL update, lets their EV boost apply to the Exp. Share holders as well. One of the Power items and five Exp. Shares can drive you the fastest. EV grinding won't be mandatory in a regular playthrough but should be for Polished Battle Tower challenges.

Best EV training spot for each stat

• HP: Swim in the water behind the counter in Cliff Edge Gate and you'll only find Wooper and Quagsire who give HP EVs.
• Attack: In Ruins of Alph the Unown give EVs in both attack and special attack.
• Defense: Swim in the small pond in Celadon City and you'll only find Grimer and Muk, who give defense EVs. Alternatively you can look for wild pokemon in Victory Road, as most pokemon there give defense EVs. If you pick the second option you might want to have a pokemon with multi-hit moves or the ability Mold Breaker, since many pokemon in Victory Road have the ability Sturdy.
• Special Attack: In Ruins of Alph the Unown give EVs in both attack and special attack.
• Special Defense: Swim in the water in either New Bark Town, Cherrygroove City or Olivine Port, and you'll only find Tentacool and Tentacruel who give special defense EVs.
• Speed: Swim in the water in Blackthorn City and you'll only find Magikarp who give speed EVs. Alternatively you can fish using Old Rod or Good Rod inside most towns, you'll only find Magikarp and Poliwag who both give speed EVs.

Trivia

• The Power items + Exp. Share combo used to be a mere oversight but has become one of the Easter eggs of the game.