It's open now: https://blog.cloudflare.com/email-routing-open-beta/

One thing that wasn't immediately clear from the blog posts --- does Cloudflare's solution allow configuration to also send emails from the custom domain email address?

In GMail (and using Google Domains to host my DNS) I've configured this by inputting various settings as per the guide here:

https://support.google.com/mail/answer/22370?hl=en

The key relevant step is: "For school or work accounts, enter the SMTP server (for example, smtp.gmail.com or smtp.yourschool.edu) and the username and password on that account."

Is that kind of thing supported with Cloudflare?

Thanks. I've been on the waiting list for quite a while. But I didn't get any notification.

You just have to apply for it for each domain you've added and they approve it within a few days