Most phone optimizers are nothing more than scams. Many of these apps also dial home. Your best bet in maintaining your S7 is to: –
1) use a file manager to delete redundant data and files.
2) uninstall apps you do not use.
3) clear your system cache, at least once a month and after software OS updates.
Greenify is a great program (that I use) whose value has been reduced somewhat by nougat and its built-in doze capability. However its impact on ongoing efficiency is relatively minimal.
If battery life is your concern then the best thing you can do is go to a black background. This will substantially reduce drain from the screen. The nice thing about android is its built-in efficiency.
One more pet peeve in android is the large number of so-called memory optimizers. These scams actually use battery power and serve no real function. Android is designed to maximize use of memory and will free memory as it needs it.