An Elite Trainer Box (ETB) is the most complete option, containing multiple booster packs along with accessories like sleeves, dice, and energy cards, making it ideal for both collectors and competitive players building decks
Effectively, think of Boseiju as a split card
Lifegain is a popular theme in Commander games, and this does what you want, giving you the lifegain trigger or a card
Is Battalion a Triggered Ability
Enabling typal synergies is great, and even if you dont hit any its still a white Elvish Visionary, which is more than playable
Ideally, your opponent should be chasing after you as you quest each turn, forcing them to use up resources to fight for the board, and making it safer for you to play your high value combos later on