Is there any reason to maintain audit columns when the target table already has an audit table?
If you are going to follow the pattern of inserting into the audit table after each insert, no there is no need to retain the creation/alter timestamps as they are present in the audit table.
However, if the pattern is to only insert into the audit table after an update/delete (this is more common), then you will need to retain any relevant timestamps/user info with the data so the original data can be copied into the audit table.
Generally, unless there is a very specific use case, it isn't necessary to store the created at/created by information as this is easily derived from the audit information itself.