I've been using this for a while for messaging. It seems to work well but it's probably not the most private.

As for your question, I prefer email for scheduling and text for day of communication. First world problem, but it's irritating refreshing email every 15 seconds after you let someone know that you have arrived at their place.

But for those last communications, I prefer text or a phone call.  Email is a little slow at that point.  I use a burner phone so I'm not concerned about using a particular app.

… encrypted emails like ProtonMail.

Thanks guys! I’m looking into burner phones. Do you know which ones do not use your real world information?