Two entities, Same ownership, Two different plan designs

Here is the situation... 

Company A & Company B are owned 100% by the same person.

Company A offers a 401k safe harbor plan

Company B offers a 401k plan with no matching at all. 

Due to the fact that the same person owns 100% of both companies would the two plans need to be identical in plan design?

Additionally, if both plans do have the same design is there any need to combine the plans as a control group with a participating employer?

Need more information. It will depend on the eligibility of each, the HCE/NHCE makeup of each, etc.  There's nothing that says they can't have separate plans, just that they need to be tested together. And if they're large enough, they might even qualify for QSLOB treatment.

@Bill Presson both companies have roughly 25 employees of which roughly 5 are HCE's.  Eligibility for both plans is 21 years of age, 1 year of service, with quarterly entry. The only real difference in plan design is that one offers a safe harbor match and the other does not. 

So QSLOB is out just because of size. Now you would have to test each BRF and see if they pass. It can work, but will need to decide if the trouble is worth it.

And even if it passes now it is easy to envision the right combination of turnover in one company and not the other to start making things not pass. 

Also, what has happened is in effect the benefits of the safe harbor plan have been made null and void by the existence of the other plan.   I have seen this plenty of times over the years.  Someone sells a person on a safe harbor plan.  The person selling the safe harbor plan doesn't do the right due diligence about the situations and doesn't uncover the controlled group and basically undoes the benefits of the safe harbor plan.