They will retain any supertypes they had
Some of the more sought after (read: expensive) cards on this list are: The original five Phyrexian Praetors Ragavan, Nimble Pilferer Atraxa, Praetors' Voice Skithiryx, the Blight Dragon The Brothers' War The Brothers War was the first official printing of serialized cards, and it was hot out of the gates with all 63 of the cards on the Retro Artifacts bonus sheet included in their sketch printings
If your commander has multiple triggered abilities, or a static ability and an activated ability with multiple conditions, that can just be overwhelming, and you wind up missing out on opportunities to do good stuff because theres just so many options
If you cast the half that has aftermath, youll exile the card if it would leave the stack
Itll also likely creep up over the next couple of years before another eventual reprint
Then, at the beginning of combat on your turn, you get to put X +1/+1 counters on another target Creature you control, where X is the number of experience counters you have