If youre interested in what some of the best cards are to open from Phyrexia: All Will Be One, we recently took a look at the top 10 most expensive cards from the set
Rebels can truly punish any opponent who is trying to play a slower game, particularly one based on one-for-one removal, by simply chaining together searchers and making it impossible for their opponent to keep up with a steady stream of creatures
Mississippi River utilizes Creative Technique and a bunch of cards with Cascade that cost six or more mana
This four-color deck is hard to discern based on the Commander cards alone, mainly because each of the cards abilities are quite different, so this may be a case of picking a preferred Commander and making some upgrades/changes to build better around that card
The most useful thing to use O'aka for is to either remove lore counters from Sagas, keeping them from finishing and sacrificing themselves, or removing finality counters