Originally Posted by harry_fine
want to get something that will give me more control, battery life, extra features.
You request is a bit vague.. what extra features are you looking for? Quite a few features require root and some require a custom kernels or recovery. The latter will trip the Knox flag. That doesn't matter to most people, but be aware that some carriers may try to deny warranty claims if you increment your Knox flag.
Towel root is the preferred rooting method for most people. It will work on pre June 6th firmware builds. You neglected to tell us what firmware build you had, but in any event if your firmware is newer than June 6th, you'd need to use the Odin software to write a pre-June 6th stock firmware to your phone first. Then use Towel root to root.
Then probably install a custom ROM that debloats your phone, making it smoother and faster, more power efficient, etc. And adding a lot of extra features and customizations. I like the Phoenix ROM for the S5. But there are a lot of other good ROMs e.g. Alliance, XtreStoLite, et al.