I am using G Suite and I had a plan to organize all my employees into groups. Rather than sharing files individually with everyone, I want to share it with a group, so that all the employees present in the group can have similar access. My question is what if I add a new member to the group, would he have access to all the files that was shared prior to him joining the group?
Yes, if you add a new member to a group used to share files in Google Drive, the new member will be able to access the files shared with the group previously.
If you later add new members to the group, they'll be able to access the document only via the document's URL. To make the document appear in the Shared with Me view of a new member's Google Drive, you must reshare the document with the group or share the document with the new member individually.