Difference between engine and engine-spring, Spring Security merging

I would like to clarify one thing, what is the difference between


and

in terms of deployment?

Is it only a matter of starting Camunda engine without and with Spring context and if I embed the Camunda engine-spring (and Camunda webapps) in my webapp will it be possible to later make my own code changes (using IdentityService, IdentityProvider and authorization) to seamlessly log-in user (in my code and using login name and password from already logged-in user in Spring Security context) to Camunda BPM without Camunda login screen appearing?

I have already managed to make my own webapp which is using Camunda engine with REST and the its security and authorization is handled by Spring Security.

In short, I want to use Spring security context in order to bypass Camunda authorization and I will be glad for any helpful tips.