1) It doesn’t have a snoozed mail feature where the mail will come back to my inbox after a designated amount of time.
Apparently GMail did not expose this API to developers, so there's no way for third parties to snooze e-mails.
The only workaround for developers is implement it the way Airmail did - with custom labels and magic. But that means you need to use the same client on all devices, otherwise snooze won't work (ie Airmail on iPhone iPad and Mac).
Since Mimestream doesn't have iOS/iPadOS versions, that avenue is also blocked for them.
Guess I'm going to stick with Airmail, for $10 per year on all devices it's quite reasonable.