[Kindle Fire HDX 7" & 8.9" Q&A, Help & Troubleshoot] GSLEON3:
Good choice. I have both tablets (well, HDX 8.9) & for someone that likes to hack things "safely" the Nexus 7 2013 is the way to go. Don't get me wrong, I have had an 8.9 HDX since release & have participated in some cool stuff, with jcase & interfaced a bit with Hashcode, learning a lot about recoveries & how SafeStrap really works & the HDX is hands down the best tablet experience when it comes to games & especially movies with the far superior SD800 & the Adreno 330, but it is dicey. You can easily brick the HDX & it is a pain to recover from bootloops sometimes. When I am not watching movies or playing a game that is graphics intensive (or just better on a big screen) I use the Nexus 7. We also have a HDX 7" in the house & while it is pretty cool, at that point, 7", I prefer the Nexus 7. It fits perfectly in the back pocket of jeans & even slacks.

Also, the N7 2013, is VERY easy to take apart, in case you have issues & need to pull the battery cable for a second. All it takes to get the rear cover off is a thumbnail & 20 seconds. You do not have to break any seals or void your warranty to check out the internals, which is great since I found a ribbon cable was to blame for my touchscreen issues.

On to your question. Rooting is really only for one reason. Modification. Whether you are wanting to add features found in an Xposed module, install custom firmware or use root apps like Titanium Backup. For rooting beginers, I always recommend using Chainfire's CF Auto Root. It is very simple & easy to use without having to download half a gigabyte. Plus Chainfire has been around a long time, providing apps & exploits that are as safe as they can be, trusted if you will, & you are likely going to be using his SuperSU app for your superuser needs. It is a good place to start because it just roots the device & installs SU. No other possibly unnecessary alterations are made. It will of course perform the fastboot oem unlock operation, but that's it, aside from SU & root.

CM is okay, but I've never been a big fan. KitKat these days is pretty darn stable & while I have added a few things, I am running stock on my N7 as it is the most stable (so are many stock based roms, like CleanRom). I run Cataclysm on my Nexus 5 & if it were available on the N7 2013, I would recommend that, since it is STABLE stock + about any useful modification you could want, without being over the top. Whatever he chooses, I would strongly recommend staying close to stock or using a stable version. Nightlies are great, if you have the time for that sort of thing & the patience to deal with things constantly added, removed or not quite finished. In the end, it all comes down to preference. I will say that once all the features are back up in 4.4.2, the Linaro based AOSPAL rom is excellent & probably one of the most customizable roms out there, but for me, I'll stick with modified stock for now.

For battery life & added features/stability, I would recommend Flar2's ElementalX kernel. It is an easy to use Aroma based install (or not if you prefer) & it is about the most stable kernel out there. Flar2 also updates & constantly works on improvements, but it is not one of those nightly updated kernels. Only when something truly functional (feature) or when faster/better way of implementing a feature is proved stable. You will also find that Flar2 is very responsive, taking time to update & explain things to those interested. You cannot go wrong there.

At any rate, just to cover everything again, here is what you MUST do to customize or flash.

1. You need to have Java & the Android SDK installed on a laptop.

2. You must unlock the bootloader:

>adb reboot booloader

>fastboot oem unlock

3. you must root, using ADB, one of the toolkits or Chainfire's CF Auto-root.

4. Install a recovery either via Goo.im's Goo Manager (install goo manager from Play Store & in menu select "install open-recovery script") or via adb/fastboot:

>adb reboot bootloader

>fastboot flash recovery whatever_recovery_you_choose.img

5. Use TWRP or CWM to back up the stock device partitions.

6. Reboot to recovery & flash or install to your hearts desire.