Having exactly the same issue here - my S7E has been pretty much superb on battery since new, but now getting major battery drain and the usual alleged culprit is Google Photos, although Android OS/System crops up in the power usage too. Added to that, the phone was often quite warm, as if it had been busy.....
Have tried many things, but with no success - usage hasn't changed, which makes it all the more annoying - although I tried this morning to Uninstall Google Photos.......so, this only removes updates et al., back to default app, and then I Updated it via the Google Store.......and, for the last hour at least, battery consumption has slowed. Too early to call it a success, but the seems promising......