Is it possible to point the gallery app to Google photos? Coming from a pixel I've always used Google and I'm not a fan of one drive inserting itself everywhere. I do like the galley app though.
Gallery only syncs with OneDrive. However, if you add your Google account to the phone, any photos you have stored in Google will show up in the Google Photos app and any photos you take will sync to Google Photos ( and OneDrive if you set it up).
Yes, I had this problem the other day. I had to copy some screenshots across from Google photos to the Gallery in order to share them. Google Photo picker doesn't work well with certain Samsung apps, this members app being one of them.