This might be a little late and hopefully of use, but I have been using the Motorola Droid Turbo XT1254 for just about 2 months and it took me until the last 3 weeks to catch this handy hidden feature to reduce the picture sizes by compression.
You can only do it in the gallery view mode, and while editing the photo, during the process, you have to make a substantive change or at least select crop and select the entire area again, then choose "export" from the three dot upper right menu and then save after choosing from the slide bar the file size.
I always found myself with 3 photos afterwards, the original in full sizes and everything, then the reduced for texting, or uploading for my Drive or website, then the "happy medium".
Then I pick the best of three and delete the rest before my backup service saves too many later on.
(Unlimited data plan with big red, and they can't stand I won't give it up!)
Unfortunately, with the Google or Android camera, I didn't have that much to offer except that the Motorola was just as good for me and I tried them both. I use the camera a lot for up close shots of disassembled or works in progress jobs to document them and catalog the work extensively and and wish I can hopefully find a way to figure this out quickly on the S5 or Note 4 or I'll be stuck with the Motorola.
(FWIW)