You cannot Mutate on a human creature All abilities of every Mutated creature are active and accounted for
Teyo works in more archetypes that the blue one, Vronos, since it's good in planeswalker decks with it's +1, and most other decks with it's -2, but Teyo is good in planeswalker decks too since he makes a free flyer to block attacks as well as Defenders, Toughness, Group Hug with his +1, Pillow Fort with the -2 to force attacks elsewhere save for one, Politics decks, and any white deck that wants pure card draw
A 0/0 ooze, upon entering the battlefield, this creature can exile any two creature cards from graveyards
What pushes Planning above and beyond such things is the current strength of delve, delirium and other graveyard based mechanisms
While it may seem arbitrary that Zell Dincht was spoiled today, there is a logic at play here
Its a little bit finicky for sure, but the deck can get enough lands in play with the same type that the March will be powerful both times you cast it