Hello,
I've been researching and wanted to ask if the Mavic 3 E can function without drone deploy and DJI Terra?

Am I still allowed to map and create routes similar to the GS Pro app that was on the Ipad paired with the Phantom 4?

Thank you

Yes.  The M3E has a basic built in capability to do that.    That having been said, I am a big fan of Dronelink.  IF you have not checked that one out, you should.  It fully supports the M3E.