Both commander choices are great for the deck, and unlike most cases, where there's a clear "best" commander, the choice between Tidus and Yuna is completely up to personal preference (although Yuna is the stronger of the two)
Best Dimir Token Commanders (The Scarab God, Oona, Queen of the Fae, and Wilhelt, the Rotcleaver) Oona, Queen of the Fae may not be a super popular commander nowadays, but in years past, it was common to see this powerful creature heading mill decks, Faerie decks, and Dimir good stuff builds due to her efficient ability to take cards away from combo decks and generate silly amounts of flying tokens from monocolor decks
Before diving in, consider what kind of trainer you want to be: Do you want fast-paced matches with hard-hitting attacks
Similarly, if the copy says that it affects an "opponent," it affects an opponent of the copy's controller, not an opponent of the original spell's controller.
While Dragon-type cards persist in the TCG to this day and find their way into one of the game's best decks (Regidrago VSTAR), the Fairy-type was removed from the Pokmon trading card game in 2020 and is unlikely to return