pokemon trading card game mewtwo Pokémon Game: Team Rocket Tin The Pokémon TCG Cyber Mewtwo Z GX Pokemon

Have 3 cards in hand

As much as this discount can stack, due to it counting wizards, there is a distinct lack of wizards in this, with only 8 being in the base deck and 9 after I have swapped the upgrades

Yes, cascade counts as casting, The rules for cascade explicitly state, you may cast that card without paying its mana cost. This means that cascade can be blanked by cards like Rule of Law or taxed by effects like Rhystic Study

For reference, before the tax was added to the Companion mechanic, as long as you upheld the deckbuilding restriction that the Companion requested, you could add your Companion from the Companion zone (your sideboard) to your hand at no cost essentially allowing you to begin the game with a guaranteed extra card in hand