mtg battle for baldur's gate set booster box Magic: The Gathering Commander Legends: Collector left corner. MTG / Commander Legends Battle

As such, unless Wizards announces that Secret Lairs will always come with a valuable bonus card, it's probably best to not expect any extra value and get a happy surprise if your drop happens comes with a bonus card on the level of Liliana, Teferi, or Jace

They then stay there and can use the abilities written on the card, as long as you can pay their cost

Since you need to be careful about your life total, you want to focus on creatures with high attack as opposed to ones with low power, as those will often take a while until they become a problem (if they even do at all)

Would I rather top deck it than a land while I'm empty-handed

With Oswalds Favorable Chance ability, every time you put a card in your inkwell you can choose to reveal the top card of your deck