[Galaxy Note 4 Q&A, Help & Troubleshooting] iridaki:
ROUNDUP OF NON-ROOT MODS/APPS/SOLUTIONS​

APPS

1. iFont

It uses the native Flipfont system present in the Note to change fonts. You can install any font from a very big list and if you buy the Donate version (which I highly recommend), you can make an installable apk for any font you want. I have already made and shared Roboto L fonts, Comic Sans and Comic Neue.

2. Adblock Plus

Works on WiFi and (if APN settings are edited) on mobile data, blocks apps on browsers and other apps. An excellent solution for ad-blocking on non-routed phones.

2b. An alternative solution that only works for browsing via WiFi networks is Adguard.

3. SMS Backup & Restore

A free app that can backup and restore your messages, no root required. Works flawlessly, I used to it to backup my SMS on my S4 and restore them to my Note 4.

4. Greenify

As mentioned in this thread, Greenify works without root as well. Automatic hibernation is even an option, albeit some issues with "talking calculator" have been mentioned.

5. My Backup

As mentioned here this app is a feature-rich backup solution for non-rooted phones.

6. SD Maid - System Cleaning Tool

This app attempts to make best possible use of its features without root present. It's a tool that cleans up unnecessary files from your phone that apps leave behind.

7. AutoStart - No root

As the name suggests, this app lets you select which applications you want to auto start after phone boot-up and it works on all phones/tablets without root permission. You can also choose one or multiple apps to auto-launch at boot with customisable delay values.

8. Busybox (No Root)

For advanced users who want to run busybox commands on their phones via the Android Terminal Emulator app.

9. Call Recorder

Call recording app that uses the Samsung standard API therefore does not require root access. It is a bit pricey but well worth the money for people who need that feature. There's a full-featured trial available from XDA so you can try before you buy.

9b. There is also a free alternative that has been reported to work well on the Note 4, AndroRec Free.

9c. Another great free alternative is Automatic Call Recorder, with the added bonus that it can record in better formats, like mp3 or wav, save on the SD card and the option for prompt to "Save or Delete" at the end of every call.

10. NoRoot Firewall

Firewall without root. Host name/domain name filtering, simple interface, fine-grained access control and no suspicious permissions on the app itself.

11. Better Wifi On/Off

A free, fully featured, ad-supported app that aims at giving you the control of the Wifi state, optimizing your battery life without losing on user experience. In theory, Wifi is less power hungry than 3G but some apps behave differently when Wifi is on (DropBox / Google+ uploads, Google Maps location caching) and the well known wlan_rx kernel wakelock is a symptom of wakeups caused by uncontrolled Wifi hotspots. The Wifi sleep policy is not working consistently and does not solve all the above problems, enter this app.

12. Helium - App Sync and Backup

Helium is the missing app sync and backup solution for Android and doe not require root. You can backup both your apps and their data to your SD card or cloud storage and sync them from your other Android devices. You need access to a computer for a brief USB connection and then you're good to go.

13. Desktop VisualizeR

Application that allows you to personalize your home screen by creating icons or widgets with your favorite photos or images, works on any launcher, even TW!

14. FREE screen recorder NO ROOT

Recordable is the easy way to create screen recordings without root. The free version adds a watermark on the recordings and limits frame rate to 8fps, but is otherwise fully functional. A Windows, Mac or Linux computer required to complete the installation (like with Helium Backup), but after this it's not needed to make screen recordings.

MODIFICATIONS

1. Full Screen Immersive Mode

Full screen immersive mode in any application or game, root is not required.

2.Enable AirView and AirGesture

2b. Instead of Nova Launcher, you can use the QuickShortcutMaker app to create any shortcut directly on the Touchwiz launcher.

3. MW-Pen App Enabler

This app that enables apps for multiwindow and/or pen window without rooted access. The only limitations are that it does not work for system apps and that enabled apps can not be updated. To update them, you need to uninstall the enabled app first, install the updated app and run it through the enabler app again.

4. Mont Blanc digital content

A guide on how to get the extra Mont blanc pens for the S Note and the two exclusive Mont Blanc wallpapers and unlock effect..

5. QuickClick

Start any action (flashlight, system toggles, media controls, etc) with a sequence of volume buttons clicks.

6. Spen Toolbox

A wonderful little app that extends the functionality of the S-Pen, by offering options for: turning the screen off when you attach the pen, changing the detach and attach sounds, creating a custom shortcut popup to appear on detach, and many more!

7. No root and want to modify your DPI? You can!

Thanks to PizzaSauce, we have a way to modify DPI without root. All you need is access to a Windows PC. Changes persist after reboot too.

If you don't want to install the whole Android SDK, you could use this tool to install ADB, which is all that is needed for this mod.