I really hate the photos program with my G6. Is there a way to remove it and have the G3 photos format instead? I don’t want Google buggering around with my pictures. Also, since I don’t have a data plan, it seems I can’t access my photos without being connected to WIFI. I could be wrong about that but that’s how it seems.
I can’t speak to the changing format/quality as don’t have either phone, however will answer your 2nd question.
Without a data plan, you would have no connection to any photo repository that offers ‘cloud’ storage.
This would leave you with WiFi to something like Google, or dump to your own PC
One can find third party gallery apps on the Google play store [I’m not currently using any as of I don’t have a recommendation]
One can access photos on the device though the photos app with out an internet connection [open the photos app --> tap the menu ( ) icon, then select the device folders]
I do recommend some type of automated backup like photos does (on WiFi) in case something happens to the phone the pictures are not lost
I use QuickPic as my photo access app.
Even if you do have cloud backup set up, your photos should still be on your phone unless you delete them and Quick Pic or any other gallery app should access them.