Implementing Inbound SMTP DANE with DNSSEC for Exchange Online Mail Flow

1. When using Smart Host routing (e.g.: https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/integrate-office-365-with-an-email-add-on-service), currently the routing back to the Exchange Online inbound connector is done by sending the message to the respective host e.g.  fabrikam.mail.protection.outlook.com. Based on this:
- Would the hosts for this use case from now on change to the respective <subdomain>.mx.microsoft?

- For the already configured domains before July 2024, after going through the DNSSEC-enablement wizard, would both .mail.protection.outlook.com and .mx.microsoft work or would it be a complete migration to another server, removing completely the .mail.protection.outlook.com? More pragmatic, if before sending to an inbound connector was through .mail.protection.outlook.com, would it mean that after the migration the new host to send to would be the .mx.microsoft one?

2. Related to the same scenario of a Smart Host, with emails being routed out with the outbound connector and then received back on the inbound, how would the new changes influence this flow? 3rd party Gateways are specified as a limitation, but in this case, my question relates to 3rd party SMTP relays.