I'm a bit of an extremist in this regard so my setup might not suit everyone but it's not that hard to set it all up. For example, I use Tasker to enable flight mode, turn Location services on and off etc. (See
here) That might be too much for some people.
But, mostly, I use a custom kernel, which is Adam in my case. I am using Wanam custom rom and Greenify. I "hibernate" all applications that I know, I won't be using often. The good thing about Greenify's hibernation method is that you're not essentially "disabling" the application. It will wake up an application if a notification for it arrives or is scheduled. It will automatically hibernate it again, once a specific interval has passed or the application is inactive.
All of this is detailed on XDA. You can find Greenify, Wanam ROM and Adam Kernel (there are other kernels as well) on XDA's Note 4 (Exynos) section. You will need an unlocked bootloader (which I think is already the case for Note 4), and root for this to work. Remember, that any kind of flashing in bootloader mode will tick your KNOX counter, which voids your warranty. You may attempt these things if you know what you're doing.