but as we all know that if more than 1 supervisor is logged in on a single layout will it be possible for them to Approve a request because it will conflict an issue of multiple users logged in and will not edit the record.
That will only be the case if two or more users have the same record open for editing. (Clicking or tabbing into a field opens it for editing.) As long as each supervisor is approving a different record, their should be no issue. And the lock applies to the Record, not the layout. When a user has a record open for editing, All other users may see but not edit that record and this lock applies across all windows and layouts that the users have open.