Hello,
As a reference, I have used this Panorama antenna manual. Your direction of thinking is correct and connecting CELL A and CELL B to RUTX11 should work without issue. It does not specify, whether A and B elements differ, thus I would assume that they operate identically. You can, of course, test them, by connecting each cell to the Main connector only and comparing mobile signal metrics from the router's WebUI. In fact, under good coverage conditions, having only Main connector attached to the antenna should yield reliable connectivity with good speeds, as Aux connector is used for reception to compensate for possible multipath signal interference and losses.
WiFi is similar, the difference being that any connector operates in the same way, thus any one can be used separately, or both at the same time for MIMO capabilities.
Best regards,