It wont affect the parent domain server, just make you have run all the prep steps in the forest:
https://learn.microsoft.com/en-us/exchange/plan-and-deploy/prepare-ad-and-domains?view=exchserver-2019
and be aware that one the new 2019 server is online, clients can "see" it so, ensure you have set the AutoDiscover SCP and client URLs correctly on the new server.