As for the latter, Vengeful Bloodwitch is the closest thing to Blood Artist we have in Standard, and its the decks primary win condition
Its building your speed from the get-go, and it has menace, so it'll probably help you damage your foes in the long run, especially on the early turns
Land Tax hasnt seen a reprint since 4th Edition, isnt on the Reserved List and fits the bill on the nostalgia front, so it seems like a solid pick for the other white slot as a super powerful card that many players wouldnt necessarily already own a copy of and services the EDH market
Wizards has stated that Universes Beyond will exclusively feature IPs not owned by the company
It's a staple in Legacy, Vintage, and Pauper, where even one extra mana in the early turns can decide games