the stack follows Last in First Out order where the last card played onto the stack is the first card effect resolved, as either player can react to these actions with other actions, such as counter-spells
This mechanic reflects how a small group of rats may not be an issue, but a massive swarm of hostile rats could overwhelm creatures they normally couldn't on their own
How well you design Magic cards has no correlation to whether youre a pro or whether youve dabbled in Pauper all your life
When a creature with both persist and undying dies, if it had no counters on it you decide the order in which both of the triggers resolve
I also am considering putting either Valkyrie Harbinger or Kalonian Hydra into this deck, but I do not wish for this deck to be too similar to any of my other decks, so I would prefer to avoid putting those cards into this deck, if I can avoid doing so, and I also am not yet certain about Doubling Season, staff of completion, or Selvala, Explorer Returned, since those cards would be awesome in this deck, but I do not wish to use them in every deck in which they would be a good addition