What am I left with after rooting?
After rooting you will still be left with stock android just with elevated privileges as you've said.

Remember, your data will be wiped, so I'd recommend doing a backup first!

If a new OS update comes along you will not be able to install via the normal Over the Air method, but you can still download the update manually and flash it via TWRP.

If you take a look here you can see all the other things you gain by rooting.