Interesting. I use Fantastical but have never really thought about using it to engage with Reminders.
I use you manually move each reminder into those folders?
Personally I’d rather be able to move reminders around within Agenda, as I find the less apps I have to review the more likely I am to do it. I’m trying to do all such reviewing in Agenda. One thing that makes it difficult is that uncompleted reminders don’t ‘roll forward’ to show in Today, so they are easily missed.