mtg cards like coat of arms (Borderless) [The Lost Caverns of Ixalan Commander] each gets +2/+2.) Coat of Arms — Rulings,

That definition isn't perfect, but it's closer than it might seem

Rafiq of the Many and The Ur-Dragon combo off to insta-kill an opponent

Especially since the printings of Ragavan, Nimble Pilferer and Dragons Rage Channeler, the steal a casting cost 1 nonland-permanent mode has become very important and overall buffed the playability of the card

Tapping a Swamp for mana gives you double the amount of mask counters on it

I think thats doable, but still hard enough that this probably needs a build around grade

Blue decks tend to be slow and patient, gradually building up card advantage and other resources until they're ready for the endgame, which is perfect for a midrange-oriented, moderately powerful format like Commander