I believe the answer to my question is no but wanted to confirm that on-prem connections can only be done using Remote Engines. Can someone please confirm? With Remote Engines we have a place to define connections and whatnot and I could not find the same functionality with Cloud Engine's. Am I correct in assuming there is no security configuration we could leverage to utilize a Cloud Engines for on-prem? Without the connection functionality it would seem the connections would need to be set up in the jobs which I can picture working fine with URLs etc but not local IPs.
It depends actually. If you are ready to expose to the web your on-prem ressource then the Cloud Engine can access it and process it.
However from security perspective, your IT ops , network team would probably deny it anyway.