Nova vs. TW is a personal choice. My wife loves TW and won't use anything but Samsung for that reason. One of the first things I do to any phone is put Nova into it.
The voice searches work differently, so some people prefer Samsung, some prefer Google.
Mail apps? I haven't found one that I like yet (and I started doing email back on Arpanet, so it's been a few decades of looking). K9 is about the closest I've found to what I like - so far. (I don't use any Exchange servers, so I don't know how well it does them.)
Don't delete system apps - once you have, and you find out that the phone won't work without that app, you have to reflash the ROM in most cases. Root the phone and freeze the app. Then, if it starts doing funny things, just unfreeze it. You can probably freeze all the carrier apps you don't use, the update app (unless you want to be one of the first ones to get the latest bugs) and any of the S- apps you don't use. (I have no use for the S Health stuff, so it's gone.)
If the phone works for a while with an app frozen, it's probably safe to uninstall that app.
But which ones to keep and which ones to get rid of? If you do a run every morning, you're going to want S Health. I don't. I don't need a pulse app either because I take my BP and pulse every day anyway, on a different device. You may want to keep it. Everyone's different. Make a list of the apps you don't use and, when you have about half your storage used, start freezing things you don't need. (Having the app installed doesn't cost anything but storage, so unless you need the space there's no reason to start getting rid of apps.)
Edit:
I'll add 2 things to erasat's post in the other thread:
1) There's no need to mass-disable apps. If you use Skype, keep it enabled. It won''t use battery by itself. Lookout should always be disabled in a Samsung device (it should actually uninstalled - replace it with another antivirus app) - there's a bug in it that will kill your battery fast unless security is disabled, which pretty much renders the app useless.
2) To keep your battery as long as possible (this is no $15, pop the back off, battery replacement phone), read
The Care and Feeding of Lithium Polymer Batteries. When you have batteries still giving you 95% capacity on a phone so old it's basically an "if I lose it I'll replace it from Craig's List for $20" phone, you'll understand how long batteries can be made to last. (My V551 is still running on its OEM batteries, It was one of the first phones to have a camera.)
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