'The proposal is due Friday. Remind me to draft it Thursday at 10.'
I see two different things here: a deadline to keep visible and an action to do earlier. I prefer the deadline in Calendar and the action in Apple Reminders. But keeping both in Reminders also has a reasonable argument: one place to look.
I'm Daniel, the maker of Second Brain. This choice shaped the app: it works with Apple Reminders, Calendar and Markdown, with a receipt to inspect each result and confirmation for pending events.
How do you handle this today? Calendar + Reminders, everything in one task app, or something else? What breaks when a plan changes?