Youll want to have multiple follow-up mutators to throw down on subsequent turns to get some extra value out of Cubwarden
Apparently Squee, Goblin Nabob is very good with Survival of the Fittest
Terastodon, Woodfall Primus, and Primeval Titan are probably the best cards for the "big green creature" role, but Simic Sky Swallower and Broodmate Dragon can serve the role as well, although they require greater deck manipulation to be able to hard cast should you draw either of them before finding your Natural Order
The easy sacrifice outlet is very relevant since you'll put Yahenni through the combat phase if all goes well
2 Sneak There are quite a few ways to get your big, expensive creatures into play through sneaky ways, though not all of them are legal in their respective formats
Enchantment subtypes (Aura, Saga, Role, Class)