As an intermediatry, Octopus provides release gating, orchestration and a overview of the stack components, and what versions have been promoted to which environments.
The parent project does not perform any deployment activity itself, it serves as the orchestrator of the child projects, providing gating and sequencing.
The child project, use the same template process, but each has the release packages that have been build to perform their technology specific deployment process.
The approach above does offer the ability to independently promote or roll-back a child component. This can be beneficial for hot-fixes, however, it is discouraged as it breaks the stack alignment principles of the release train.