Advantage+ placements by default, manual when you have a reason
"Let Meta explore first, learn what works, and only then take manual control if needed."
Create > Awareness > Continue opens the ad-set editor with the two options. Advantage+ uses Meta's data to find cheaper results than guessing. Go manual when the creative only makes sense in one format (a vertical video for Reels and Stories) or when data shows a placement wasting money. Value rules (create a rule set, acknowledge "cost per result may increase", pick placements, optionally raise the bid) let you weight placements without switching them off - shown but not explained in depth.
The default protects beginners from starving Meta of inventory.