You do have a significant set of challenges. I am 73 with both shoulders replaced conventionally, one 5 and one 7 years ago. For me, the most recent of these shoulder replacements is a continuous messy recovery but the original pain is gone. The pain now is from efforts to operate the shoulder in its proper position instead of up and forward as it prefers. Range of motion is returning as the uncomfortable exercises slowly do their magic. PT, acupuncture, Tai Chi, daily yoga, relearning swimming: all have returned me to a much younger energy level of 20 years ago. It is not a comfortable process but I wanted to avoid the necessity of re-opening the shoulder for a reverse replacement as perhaps should have been done initially. For you to do both simultaneously would be a huge shock to your body and life energy. You are a trooper if that is your chosen route. I understand the benefits of reverse shoulder replacements but have not directly experienced them. Be confident that your surgeon will guide you on the right track. That said, they are focused on their version of the cure.

In my case they did repair some rotator cuff tears while doing the replacement. The shoulder is essentially immobilized after surgery anyway, thus protecting the cuff repairs. The joy of the reverse joint, from what I understand, is a more rapid return to functionality, avoiding some of the joint stability and range of motion problems I have experienced, now mostly solved (85%) after a long drawn out process.

As an aside, what I personally have found is that the habit of indexing or registering one’s scapula before and during shoulder movements is an important way of avoiding further shoulder problems and rebuilding mobility. Consciously thinking about moving the shoulder blade down and back ( pinching them together if both available) is often overlooked when discussing arm movements. It may not be appropriate for some rotator cuff injuries, but eventually I hope it will be a habit worth remembering as your recovery proceeds.
And I must add that having to use the non dominant side was a refreshing skill to learn, leading to a more general feeling of well being
Once again, be confident that your surgeon will guide you on the right track
My struggle continues, as I slowly reap the benefits
I wish you a speedy recovery.

Mike