How does an eligible participant "opt out from year to year" on a CB plan? Either you satisfy the accrual requirement and get a benefit or your don't, it's not a CODA.
But assuming that there was some amendment timely and properly executed such that no HCE benefits under the plan, or no HCE worked enough hours to accrue a benefit, then as CB Zeller pointed out you will automatically pass gateway and 404(a) because the HCE rate is going to be $0 and 0%.
Assuming the Plan's are not top heavy then if no HCE benefits for PS or CB than your PS could be $0.
If the combo plan is top-heavy, RTD on how you satisfy that in your specific situation.