One of our clients is migrating from a traditional file server and a separate Dropbox account to using Teams and SharePoint. They already have a traditional distribution group called Sales, and the new Team/SharePoint will also be called Sales. We're looking at upgrading the distribution group to an Office 365 Group before we start so that we can pair the new Team and SharePoint site with it.
The only catch is that a few of the distribution group members don't need access to the files that are being shared. They only need access to the email/messages. There's also one or two people who are not currently in the distribution group but will need access to the files but not the email/messages.
What's the best practice for setting up this sort of granular access? Even though these are people within the organization (but in different departments), should I set them up with guest access?