I would not be very excited about that last one either while enough planeswalkers exist to fill out your deck, the lack of ramp, instant interaction, and just cheap spells in general would make it torture to play
On the other hand, even if you cast the 3-mana cost "Delayed Blast Fireball" for its foretell cost of 6 mana, the mana value remains 3, and even if you cast the 4-mana cost "Legacy of the Legacy Warriors" for its overload cost of 8 mana, the mana value remains 4
Templar Knight is whites Shadowborn Apostles/Dragons Approach
Izzet Spellementals (10.5% of the Winner's Metagame) 6 Island 4 Riverpyre Verge 4 Spirebluff Canal 4 Steam Vents 4 Eddymurk Crab 4 Hearth Elemental 4 Sunderflock 4 Opt 4 Prismari Charm 4 Sleight of Hand 3 Burst Lightning 2 Get Out 2 Traumatic Critique 2 Spell Snare 2 Impractical Joke 2 Stormcarved Coast 2 Flow State 2 Winternight Stories 1 Spell Pierce 3 Colorstorm Stallion 2 Annul 2 Ghost Vacuum 2 Slagstorm 2 Ral, Crackling Wit 1 Disdainful Stroke 1 Flashfreeze 1 Octopus Form 1 Spell Pierce Izzet Spellementals is built around a high density of cheap instants and sorceries that draw cards, interact early in the game, and stock the graveyard for Eddymurk Crab and Hearth Elemental