Email Template Client Compatbility?

Comparing with Moscaio (FOSS), which provides base templates and WYSIWYG editor, how does Ghost compare in terms of email client compatibility. Ditto for MailChimp.
It is the claim of many newsletter tooling that they’ve done a lot of extra work to ensure the diversity of clients out there (Gmail, Outlook, etc) can consistently display the emails they receive. How do we know the level of compatibility when considering migrating to Ghost as a newsletter tool?

Also, how do we know the level of compatibility between the email templates and Ghost? That is, we can start crafting a newsletter with a branded or stock template (which includes enhancements for mail client compability). Can any of them be used to craft emails in Ghost?