The following are six best practices for SharePoint Online:
Branding - In both the classic and modern SharePoint Online experiences, several default themes and site designs can be utilized.
Information Architecture and Hub Sites - With a modern SharePoint Online experience, every site is a site collection which can be associated with a hub. The hub is essentially a like collection of sites which share navigation, branding, and other elements.
Modern Experience - In SharePoint Online, the modern experience is flexible and easier to create beautiful, dynamic sites and pages that are mobile-ready.
Navigation - In SharePoint Online, effective navigation helps users find what they need quickly. Such principles should be followed for both classic and modern based sites and page navigation.
Performance - The modern experience in SharePoint Online is designed to be easy, compelling, flexible and responsive which thus lends itself to better performance.
Permissions and Sharing - SharePoint Online has an easy interface as far as a way to permission and share sites to those individuals who need to see and utilize information.