Applied to Visual Studio Development : we’d rather run the In-process model (function code runs in the same process as the Functions host process, using .NET runtime) than the Isolated worker process (function code runs in a separate .NET worker process.).
Develop Azure Functions using Visual Studio | Microsoft Learn
Choose the worker mode : isolated worker vs in-process
Work with app settings locally
During local development, these settings are instead added to the Values collection in the local.settings.json file. The local.settings.json file also stores settings used by local development tools.
Visual Studio doesn't automatically upload the settings in local.settings.json when you publish the project. To make sure that these settings also exist in your function app in Azure, upload them after you publish your project.
Remark : The values in a ConnectionStrings collection are never published.
Azure Functions: how to debug remotely in production – Stefano Demiliani