There are many ways to build the web; most of the ways can be implemented in AEM, which one works best is going to depend on your authors. What the authors are willing to author, how involved do they get with content, and how involved do they want to get with crafting experiences?
SPA - single page application an alternative to a multi-page website. SPA Editor - AEM native editor for SPA’s Headless - a pattern where you leverage API or GraphQL to get data from server Widget - a component of a web page with clientside experience, it has basic HTML, and javascript turns into the interactive experience when loaded.
AEM Content Service -
AEM’s Content Services leverages traditional AEM Pages to compose headless REST API endpoints, and AEM Components define, or reference, the content to expose on these endpoints. AEM Content Services allows for the same content abstractions used for authoring web pages in AEM Sites, to define the content and schemas of these HTTP APIs. The use of AEM Pages and AEM Components empowers marketers to quickly compose and update flexible JSON APIs that can power any application.
You should refer below for more information -
https://experienceleague.adobe.com/docs/experience-manager-learn/getting-started-with-aem-headless/overview.html?lang=en
https://aem.design/blog/2021/09/10/spa-headless-widgets-and-aem