Develop using SharePoint Add-In or SPFX Framework?

Dear Yarrah

I can tell you that you are in the right place, so keep calm and talk together 🙂

SPFX solutions can be published on any tenant, however, it is essential to follow best practices, but this applies to any approach.

SPFx Custom Webpart (dashboard?) must be deployed to tenant app catalog or site collection app catalog https://docs.microsoft.com/en-us/sharepoint/dev/general-development/site-collection-app-catalog

SharePoint assets like lists, content type could be deployed already using SPFx https://docs.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/get-started/provision-sp-assets-from-package or using PnP Provisioning engine https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/introducing-the-pnp-provisioning-engine

SharePoint Add-ins approach is already valid, in my opinion, it depends on technology approach, architectural approach and dependency, and isolation/security (governance) level you want to introduce in your solution.

What I understand, your SPFx WebParts and Custom lists is a classic solution you could easily deploy and maintain everywhere, in every tenant.

If you can, please check already Implement Continuous Integration and Continuous deployment using Azure DevOps  https://docs.microsoft.com/en-us/sharepoint/dev/spfx/toolchain/implement-ci-cd-with-azure-devops in order to understand the great potential of how to build a solution with SPFx and deploy/maintain it according to the DevOps principles.

Cheers,
Federico