merges to the integration branch instead of working directly on the integration branch...How it works in RTC

In RTC, you normally do not work "directly on the integration branch" (if by "work directly", you mean "checkin to").   You checkin to a repository workspace, and then when you are ready to do so, deliver those changes to the integration stream.  The exception is when you use the web browser client, which lets you commit changes directly to a stream.

In addition to Geoff's answer: if you have changes on a repository workspace and you need them on a different stream (call it branch for now) then you add that stream as a flow target and point to it as current flow target. You then see the differences between your repository workspace and the stream and can integrate them.

Your repository workspace is usually synched up with a stream and that is how you bring data from one to another stream.