If you have back issues, you might seriously look into recumbent (bike or trike).
I have mild (now, used to be worse) back issues, and switching to my recumbent bike really made a huge difference in ride comfort. Recumbents have actual seats, not saddles.
Of course, that road led to needing (needing, I tell you) to get a velomobile. Now I almost never drive any of my vehicles.
