best method to cancel playstation plus?

games you downloaded from the extra or premium catalogue lock as well, not just the monthly ones. your saves on the console are fine. cloud saves hang around for a while after it lapses, but i'd copy anything you care about down to the console before it ends.

You don't really cancel it, you turn off auto-renew. On PS5 it's under Settings > Users and Accounts > Account > Payment and Subscriptions > Subscriptions. You keep Plus until the end of the period you already paid for, and the monthly games you claimed just lock until you resubscribe.