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You can look for Default Applications in Settings (I have a Note 3)
or
Applications Manager - All - Touchwiz Eazy Home - App Info screen, clear default
and Touchwiz Home, default set.
It has been annoying for a lot of people on previous TW versions, but it should settle down.
You should also have Applications Manager - Menu - Reset App Preferences, but this will give you a warning that it will enable disabled apps and reset other defaults until you set them back individually.
I used the stock Touchwiz Home launcher for a year (Touchwiz is more than a launcher) but finally started to use Nova Launcher permanently (only to add more icons on my main Homescreen), and it's very easy to switch back between Nova and Touchwiz.
