Hi,
It is not clear in the January 2021 update of the Nexus Guide if the Nexus Sprint Planning replaces the Sprint Plannings of the Scrum Teams. It is clear for all Events, but not this one.
Quotes from the Nexus Guide:
Appropriate representatives from each Scrum Team and the Product Owner meet to plan the Sprint.
a Sprint Goal for each Scrum Team that aligns with the Nexus Sprint Goal