How to properly organize the file storage structure?

Question

NAS

Hello.
Input data:
Synology NAS / disks in raid 1 / two partitions: one for file storage, the second for backups / authorization via AD

It is necessary to properly organize the file storage in terms of data storage security and access to them.
What has been done so far:
The Users folder has been created and each employee's personal folder is in it, the employee has access only to his own folder (read / write).
A folder for Departaments departments has been created and department folders in it, an employee has access (read and write) only to the folder of his department, all accesses are regulated by AD security groups.

Actually questions:
1.na what to pay attention at the organization of access to files from the point of view of a practicality and safety of access?
2.If an employee (1) needs to send a file to another employee (2), how to organize it correctly? I read that creating some exchange folders with access (read and write to all users) is undesirable. Then what is the right way to do it?

Answer 1

Let the files be sent to each other by mail.