Hey @Muhammad Hammad Naeem thanks for the question
In the end runbooks are just PowerShell (or python etc, depending on which type) but there is a learning curve to using azure automation. The advantage is that once you're comfortable with Automation then the scripting is little different from just using PowerShell in a regular terminal window.
Logic Apps is simpler in the sense you don't need to code, you can start a logic app based on a scheduled trigger and you could use the http trigger action to send an ARM REST API call to resize your web app. Logic Apps consumption would be the right place to do this. Managed service identity would need to be assigned to the logic app with permissions / RBAC to change the sku on your app service plan.
You could use Azure function in a similar way to automation, using a scheduled trigger and here too you could use script directly as functions support powershell. Again, you'd want a consumption function (to avoid cost) and a managed identity with the correct RBAC to the web app plan.
However all 3 have a learning curve and anything you do against the control plane in Azure needs to be authorized, for running code that would be best via a Managed Identity with the correct RBAC permissions (in the same way , as an end user you need the right RBAC to change the plan tier via the portal UI).