Thanks so much. Lots of food for thought
My daughter said that you need multiple backpacks. One for the flight and another as a daypack.
It’s for my husband to carry as his personal item. He will be carrying all the stuff that I need him to carry 
. One being my CPAP, and yes I know I could carry it separately but I’m a)paranoid that I’ll forget it in the overhead bin that I can’t see into and b)my husband hates multiple small bags. So he can carry it and the rest of the stuff that he needs.
I have a MZ Wallace backpack that I love and spent a lot on. The CPAP takes up the entire pack and leaves room for very little else.
We will be on a cruise, my husband hates to carry a bunch of stuff around for a day tour. I have a crossbody bag that holds a lot. So I don’t think I will utilize a smaller backpack.