When planning for your site collection architecture, you'll need to make some decisions about the design. These decisions include the following:

• The organization method for site collections or hub sites: Common organizational grouping methods include business regions or locations, product or business groups, agencies or departments, and external collaboration partners.
• Site templates: Once you know how many site collections you need, you can determine what kinds of site templates to use. For classic SharePoint architecture, this could include templates from the Collaboration, Enterprise, or Publishing site groups. For modern SharePoint architecture, the two most common templates are Communications Site and Team Site.
• Storage: When you purchase a SharePoint Online subscription (either standalone or as part of an Office 365 suite), your tenant is automatically allocated a pool of storage based on the number and type of user licenses purchased. Storage is automatically allocated by default, but you can further adjust or limit the storage as your organization requires.
• Language support: If your organization needs to support multiple languages, you may wish to use the Multilingual User Interface (MUI) feature to allow users to view sites and pages in a language other than the one configured for the site or site collection. 

• Governance: Perhaps the most often-overlooked planning task, governance is the process of deciding things such as permission models, managing external user access, rights management, common user interface and design elements, the amount of customization you allow administrators to perform, how search works, retention, and site life cycle management.