Email. All my notes, plans, todos, reminders (via snooze/send later) are in the email. I also use calendar to keep the family in sync. My current "life database" (i.e. inbox) is on the iCloud (like everything else, so it is good for Legacy Contact, when I pass away), though it was in google workspaces before and it can be on anything else in the future (including self-hosted server).