Hi @Lipi ,
SharePoint Online doesnt really enforce license requirements, so users without license can still access content. Permissions are not dependant on the license either, if you want to restrict them use the SPO permission model. Internal users without licenses will be able to see content to which they have permissions, but will not be able to make any changes.
External users will be able to do whatever they have been giver permission to do.
You don't need to assign licenses to external users, please refer to the following document
https://learn.microsoft.com/en-us/sharepoint/external-sharing-overview?redirectSourcePath=%252fen-us%252farticle%252fManage-external-sharing-for-your-SharePoint-Online-environment-C8A462EB-0723-4B0B-8D0A-70FEAFE4BE85
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