There is no free tier - just sample playlists.
I tried doing embedded songs in the newsletter, but most email clients, such as Gmail, strip out the embedded HTML for security purposes. I can create a link, which I might start doing, but we'll see.
I currently make my playlists on Spotify. But I have issues with them, in particular, that they colluded with the labels (who got equity in Spotify) to keep artists' payments artificially low. Also, I know there are a lot of Apple-heads out there. So I am supporting multiple services. In order to port the playlists to other services I have to have an account there, so if you want me to add a service, let me know.