Are your parents still in love? Or have they gotten to the point where they find relief being apart? Is one dependent on the other? Do they have an "enabling" relationship? Are they two different personality types in such a way that "helpful" care is defined in two very different ways? These are the questions your "geriatric care manager can help you answer.
My parents needed very different kinds of care. My mother had end-stage cancer and was physically failing, but was sharp as a tack mentally. She needed to feel she had some control over her life. I provided her with a "log book" to record what was happening and it soothed her agitation, as well as keeping the staff alert because they knew she was keeping records.
My father simply "went with the flow." As a result he got VRE (see the CDC for a definition) and it complicated where he could be placed. He needed more custodial care than my mother and ended up in an "Alzheimer's unit" for several years.
My suggestion is that you try for a "continuing care" facility. See if they can share a bedroom. Then the "weller" one can spend the day out being stimulated appropriately while the "sicker" one receives the treatment they need.
Blessings on you and good luck.