Abe let your HTML pure: Nothing is added to your templates. The Sitemap plugin helps you inform the search crawlers about your pages. Free the SEO !
Just configure the deployment you need, choose between amazon S3, Surge, Github, or any (S)FTP reachable server, and you're good to go !
Manage your users and their authorizations
Creating your user database and a custom validation workflow ? It's one json away. Give rights en permissions to your users in a blink! AbeCMS is using oAuth2 (of course)
Focus on the content and only the content. You're able to create posts in a snap... The content is saved as JSON and exposed through REST endpoints !? What ?! Abe is Web and mobile apps ready ? Hell yeah !
And as your needs are specific, you can use existing plugins from others or create your owns. Algolia, Asana, Google Maps, PM2... Yours... What else ?