Can some fields be visible only for certain groups of users?
Yes. To do this you will need to create multiple versions for your sheet, because in this type of use, the sheets usually look different for different groups of users.
To create two versions of the same sheet, first right click on the sheet, or click on the little arrow when you hover on a sheet, and choose "Duplicate Sheet". (You can also access this option from the Sheet Linking Tools. Ragic will create two sheets of the same name, fields, and everything. These two sheets point to the same set of entries in the database; when you enter a new entry in one, it will also appear in the other. All edits and deletions will also be on both sheets.
You can change the access right for these two sheets, you can set up one sheet visible to one group, and the other sheet only visible to the other group of users.
You can go to Change Design for both sheets, and add and remove the fields that were intended for different groups of users, which will let different groups of users see different versions of the same sheet.
For more Information, please check out our document on how to create multiple versions of a form.