Yeah... but how many of them are perfect duplicates?
I tried likewise S5 twice in about 4 month gaps in between and both times I've had major issues with it, the second time I couldn't even download anything on the playstore on my data...
OK.
You got two subjects there if I followed you, I'm just going to address the first one.
To clarify, let's define root - root is the exact same thing as administrator access on your pc. The name of the admin account in Windows is Administrator, on Unix machines that account is named root.
Android is based on Linux (the desktop operating system), it's just a small version but it's Linux and Linux is from the Unix family - so it's root.
In this discussion, read my words twice if you want and where I say root, go ahead and say to yourself - admin.
Right now, Samsung and/or your carrier has root access to your phone.
And they use it with every OTA update.
There's a hidden piece of software under the hood that doesn't run so you can see it called recovery.
An OTA update is just a zip file containing some system stuff and a hands free installer - just like a pc, it needs an installer to install things.
Some stuff on your pc you install as admin by right clicking the install file. Etc etc etc.
On your phone, after the update downloads, it does its thing, often with a reboot and recovery runs - it recovers the update zip file and runs the installer. The password is encoded as a security signature in the zip file that no one has ever cracked.
So.
The first thing you do is use some tool - often just the one directly from Samsung and replace the built-in recovery with a "custom recovery."
It has either a simple or fancy interface just for you - you can see it and you can install zip files from the development community, no secure encrypted signature required.
At this point, you can just add the piece you're missing onto your current TouchWiz (rom) by installing a package called SuperSU.
It contains a binary library (under the hood stuff) and an app. That's it. Install that and boom, you're rooted. Everything stays the same.
Except - you can run apps requiring root access or get to hidden areas of your phone (only after you're an expert and not a second before).
When you run any root related app or operation, the SuperSU app blocks it and pops up a dialog for you - root access for XYZ: disallow, allow, or allow once. In the vernacular, root access is superuser access, superuser is the descriptive class for any operating system administrator or root or purple ponies account. Hence the name SuperSU. (Improved superuser from the old Android days - it's super superuser lol.)
You are now running a stock rooted rom.
Alternatively, you can install an entire rom with superuser already included.
Those will be TouchWiz based or other, as funky said.
TouchWiz based is what the name implies - not a perfect copy because you can do that yourself without a full rom installation.
Developers are users too, so they might start with TouchWiz and improve it as they see fit.
If it's a good developer, a lot of people agree and the rom becomes popular.
Ditto on the non-TouchWiz roms.
What if a rom is screwed up or screws up your phone?
You don't care.
Because you have read, read, read and read some more, despite what anyone says, you're first act after installing custom recovery is to use a root feature that your stock recovery does not have - you make a nandroid backup of your phone.
It backs up your entire working phone - TouchWiz, your apps, data, settings, the whole enchilada.
You restore a nandroid backup and it's like stepping through a time machine to the place you were before you messed around - only the custom recovery stays in place (along with other goodies down at its level like your radio firmware and so forth).
That's the big picture, there are a lot of details to it but that's generally it.
Rooting is not a cure all - it's just a gateway to performing admin level changes - that you have to pick out to suit your needs.
