The cards you choose can be ones that were just milled or ones that were already in the graveyard
Now, technically, not using the "choose one" text makes the card play different in certain scenarios (for example, a Naturalize can be redirected from an artifact to enchantment where a modal card cannot change modes when redirected), but for most practical uses they are almost identical
Archetypes like the Lurrus of the Dream-Den-less versions of Boros Energy or Domain Zoo can benefit from it in the Sideboard and punish the recurrence of Timeless' greedy mana bases
A PSA 8 on a $200+ card still holds value, but the premium over raw is modest (10-20%) PSA 9 (Mint): Nearly perfect with one minor flaw perhaps slightly off-center or a single corner with minimal whitening
Your deck can only comprise cards of two different ink colours (Amber, Amethyst, Emerald, Steel, Ruby, Sapphire)