3D Touch can be used with your own measure of how hard you want to press into the screen. The settings are available in the "Accessibility" section (why it's here, Apple? Why not in the Settings tab?).

I find that I'm fine with "Medium", although others cant master it and prefer to use "Light" instead. I find that "Light" makes it more likely for me to activate the "jiggle to uninstall apps" than "3D Touch". "Firm" is like really pressing hard, and I wouldn't advise using this, especially for ladies (or Ah Bengs) with long fingernails.

That picture below, you can test and to try how sensitive you want the 3D Touch to be, which is perfect to use the "Peek and Pop" feature. The pressure recognized is analog in nature, meaning that it does not register pressures as 1s and zeroes or a light switch (on and off), it detects increasing pressure as harder you press. Press in firm the picture pops into "preview" mode at full screen, press in even firmer, the photo pops into "Photos" app for full manipulation.

4K recording has been steady and pretty consistent in the OIS department. It may seem that color is much more pleasing on AMOLED screens on Samsung devices, but upon reviewing them for editing on my Mac, I'd prefer the iPhone's 4K recordings, less sharpening, soft natural quality to them.

LivePhoto is nice, I left it on still for not having to worry about storage space on this 128GB model. I'd consider leaving it off for smaller capacity models. LivePhoto thumbnail scrolling has this nice stop-motion quality to it when viewing through them, makes them stand out against all the normal still shots of the past.

Touch ID almost feels like a button now instead of a scanner, the moment you press it in, it grabs your fingerprint scans so fast, you'd swear it's works like a button already. For making sure it's not a fluke, I tried to see if it does unlock on an unscanned finger, and nope, it's a lockout.

"Blazingly fast" would be the word I'd describe it. Bear in mind the iPhone 6 Plus isn't a slouch, but keeping up with my typing would be a task for the 6 Plus on iOS 9, the 6S Plus does that and keeps 20+ odd apps running in the background (during first setup I had more than that, approaching 30, to cross log-in between apps that signs in with social media credentials), and it is as fast as when I first opened it out of the box.

I rarely game on this, other than for the occasional Crossy Road and the new "The Martian" game with Apple Watch support on it. Battery life has improved so much that I'm comfortable leaving my Anker battery pack at home and travel light when I'm in town, even when the iPhone is tied to my Apple Watch via Bluetooth and notifications streaming in.