New Work Item -> New Feature Branch. How should I deploy these changes?

I created a very simple pipeline connected to an existing repo in GitHub hosting a Salesforce DX project. The "Production" stage is tied to my production org, and there is a single org tied to "Developer Environments" which is a Developer Sandbox (called "Carlos Developer Sandbox").

Screenshot before activating:

Screenshot after activating the pipeline:

I created a test work item in the project tied to this pipeline, and set this work item to "In Progress". This creates a feature branch (in this case, gs-salesforce/WI-000001).

Screenshot from the Work Items screen in Salesforce:

Screenshot from GitHub:

**What is the intended user journey now?** Should I:
1. Pre-requisite: have ensured that my default git branch of the git repo hosting my Salesforce DX project is synced with my production org?
2. Pre-requisite: [have back synced](https://help.salesforce.com/s/articleView?id=platform.devops_center_run_back_sync.htm&type=5) (through DevOps Center, see screenshot below) my development environment(s) with production prior to have set this work item to in progress?

3. Make programmatic (code-based) changes in this feature branch?
4. (Somehow, and _**outside of Salesforce DevOps Center**_) deploy these code changes from my feature branch to the org associated with this work item (in this case, a Developer Sandbox)?

[alternatively to (3) and (4): make changes to the development org associated with this work item through declarative (point-and-click) development (aka [ClickOps](https://controlmonkey.io/resource/what-is-clickops/)), and then use [DX Inspector](https://help.salesforce.com/s/articleView?id=platform.devops_center_dx_inspector.htm&language=en_US&type=5) to [commit these changes](https://help.salesforce.com/s/articleView?id=platform.devops_center_commit_changes.htm&type=5) into my feature branch]

5. Verify things work in my development org, and then, _**in Salesforce DevOps Center**_, promote this work item to the next stage (in my case, the next stage being prod)? And Salesforce DevOps Center therefore does the deployment and also the commit back to the branch associated with the next stage?