It's pretty easy to cast noncreature spells in this deck, and it really doesn't matter what they are if we're also getting a copy of our best creature in the process
Riveteers Charm is even an instant, so you can play it on the opponents end step to have all your mana available the following turn to cast the cards you exile with it
Eladamri, Korvecdal serves as a nice card advantage engine in a deck with a lot of creatures
You can also slow things down for your opponents by tapping Archelos, so that only you get the upside during your turn, and you can do that by using cards like Cryptolith Rite, convoke spells, or some auras or equipment that requires you to tap a creature
Just for mono-green Commanders alone, Sphere Grid fits in six of the top 10 Commanders despite only three of them having +1/+1 counter synergies
Journal of the Prime Izmagnus Theres no other joke out there that summarizes Izzet better