Heres how it works, and why some are a cut above the rest
You dont need to perfectly balance the CMC of your cards with your mana base, but you will want to keep each colors CMC and mana base percentage within 10% of each other (reduce this percentage a little if youre playing with 4 or 5 colors)
Of course, youll need to slide them out of the sleeve and turn them over when they flip to their other side during play, so its definitely best to opt for the highest quality sleeves just so you ensure theyll hold up to repeated handling of the cards
Its a massive creature that comes out on turns 1 to 3 on average, and it brings immediate and assured value in drawing you seven cards
Thus, having a Commander that has the best staying power allows you the time required to build up into a lethal attacker
If you leave the game, the exiled cards remain exiled face down indefinitely