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Own the offshore company personally or through holding offshore company?

This depends very much on how your Offshore company structure should look like and how much risk there may be involved in the business the company will conduct. In some cases in may be enough with 1 layer while in other cases a 2,3 or even 4 layer offshore company structure may be useful.
 
Yes in most cases it would be best to form a Seychelles (or other Offshore holding company) holding company and thereafter register a trading company which either can be offshore or simply onshore, depending on what goals you try to achieve.
 
In regards to the local holding, then it is true, many are using this structure for tax reasons.