Should I upgrade my iPhone 6s 16gb? Is this iPhone storage potato for today?

Overwatch Rules
23.01.2018

SRΛSC
23.01.2018

For most, it wouldn't be enough but its a matter of it is for you. I personally would though.

Will a 16GB iPhone 5 have 16GB of space? I want to get an iPhone 5 and the 16GB will suffice, however I'm concerned about the actual space. I have a 32GB iPod Touch but according to iTunes the maximum space available is 28.5GB. Could I expect this sort of thing to happen on the iPhone?
Should I stick with my Note 3 or upgrade to the iPhone 6S (16GB)? So I've had the Note 3 for about a year and wish to get back on iOS, mostly because of my peers and I really like the iPhone. But practically the Note 3 has a much larger display and a bigger battery capacity. IIm really confused between the two. Is it really an upgrade spec wise or am I losing something in the bargain? It's an exynos version BTW, so there's no 4K recording.
My new 16gb iPhone 5s' storage doesn't equal 16gb? I bought a 16GB iPhone 5s and when i go to Settings > General > Usage, it says i used 2.3 GB and i have 10.6 GB available. And that would equal 12.9 GB. Shouldn't it equal 16GB?
My iPhone 6 has turned into a potato after iOS update I can't click the phone application in order to make calls, listen to voicemails, and add contacts. It freezes my phone everytime I open it and then it crashes. My phone has slowed to exponentialy slow speeds, it freezes almost every 15 seconds when I'm using it, my battery drains from 100 percent to 10 percent within 30-45 minutes, it's ridiculous. I updated to iOS 11.2