One of the events that is usually disregarded by most teams is the 2nd part of the Sprint Planning. And yes, if this is new to you, the Sprint Planning is a 2 step process.
Sprint Planning answers the following:https://scrumguides.org/scrum-guide.html#events-planning
What can be delivered in the Increment resulting from the upcoming Sprint?
How will the work needed to deliver the Increment be achieved?
The 1st part is the one everyone does and knows. The PO brings a challenge to the team for the upcoming sprint and together collaborate to get all the PBI needed for that goal. And that’s it, at this time the PO work should be done (more or less).
The 2nd part of the Sprint Planning is the actual plan. The team now looks at what the goal is and the PBIs they have and come up with a plan on how to deliver them. The team at this point owns the Sprint Backlog, so they may pull in new items, create or delete them, anything they feel they need to do to achieve the goal better.
This is very rare to see a team do. What most teams do is they have this discussion on an item basis as they pick them. The problem with this is, we do a Sprint Filling, not a Sprint Planning.