[General Questions and Answers] Planterz:
Yeah, that's normal. TouchWiz is a very heavy ROM, with lots of extra features, which means lots of processes running in the background. S Voice, S View, S Finder, gesture controls, etc. And if you've purchased from a carrier on a subsidy or payment plan, that means you'll have some carrier bloat running too. Some only a handful of MB, some take more, but when you have so many running at once, it all adds up. On my Galaxy Light (a lower end device), 700-800MB of the 1GB RAM is typically taken up. On my Note 3, which I've barely done anything with yet, .9-1.5GB can be used up pretty easily without any multi-tasking. Obviously, the Note 3 has many more features, which needs more RAM. TouchWiz is very heavy, which is why most of their newer mid-end models have been coming with 1.5GB RAM instead of the "standard" 1GB - one gig just isn't enough to run TouchWiz, even though it's plenty for stock or near-stock phones like the Moto G.

What you need to understand though, is that even if 1.2GB RAM is used up, that leaves 500MB or so for all the apps you'll be wanting running in the background. Facebook, Words with Friends, the camera, music, etc. That's actually quite a lot. Also realize that "no apps running" does not mean that no apps are running. There are LOTS of apps running (every feature/function is an "app"), but they're not ones that you've loaded, but they're part of the "system", so they're already running and can't be killed. Facebook is one you've loaded. Smart Screen is not, but if you have it enabled, it's still running, and it's still taking up some RAM.

What you also need to understand is that you

want

these apps running in the background, taking up your RAM. And you don't want to be using a task killer like Clean Master to obsessively free up RAM pointlessly. When an app like Facebook is running in the background, it's quickly retrievable. Kill it, and next time you want to load it, it has to load from the internal storage into the RAM again, which takes time, processing power, and battery life. You can still use a task killer like Clean Master to free up some RAM if things get sluggish, but it's best to white-list the apps you use a lot so you're not constantly loading them from storage and killing your battery and wasting time. Or, if you were playing an intense game for a while, but don't plan to again for the rest of the day, by all means kill it with the task switcher. Android actually does a very good job of managing your RAM, and except in certain circumstances, it's best to just let it do what it does by itself.

If you can't help but obsess with free/used RAM, or you actually multi-task to the point of things getting frustratingly sluggish, turn off all the features you don't need or rarely/never use. Go into your app manager and disable (Turn Off) apps/features you don't use. Find a "de-bloat" guide for your phone and find out what's safe to delete or turn off. This includes Samsung crap, carrier crap, and even Google stuff as well. If you don't need Lookout, disable it. If you don't use Google Wallet, disable it. Samsung Print Service? You don't use that. Disable that crap. Some of these wouldn't be running in the background anyway, but it's easy to accidentally load them, in which case they'll needlessly be taking up RAM.

---------- Post added at 09:22 PM ---------- Previous post was at 09:18 PM ----------

I cross-posted with your edit, but you've found some of the reason. As I said above, you want your apps running in the background, taking up RAM, unless you don't plan on using it again for a while. The other reason, as I said, is that heavy ROMs like TouchWiz, LG's Optimus UI, Sense, etc, have a lot of features and running processes compared to stock, near-stock, or the custom AOSP ROMs.