Stock Rom -> CM12 with TA Backup.. Making sense of all the Guides :)

Greetings,

I have for the last few days been reading though a lot of posts on this forum containing guides for howto root, backup TA, unbrick and installing custom ROM etc.
I must say, I am getting a little confused, because they there seems to be a lot of different guides and methods, some seems old and (perhaps) outdated, some are very easy and other very complex in comparason.

So, please forgive me, but I would just like some advice on the current best and easiest way of performing what I plan.
I am getting both a Z3 Compact Tablet Wifi (Hence why I am posting on this forum) and a Z3 Compact Phone. So both Stock ROM and locked bootloader.

For the Tablet I would like to Backup TA, Unlock Bookloader and install CM12 w/ Google Apps Nano (Or what the smallest GA Package is)
For the Phone I would like to Backup TA, Unlock Bootloeader and Install CM12 (No Google Apps).

But First a General Question:

I get the impression that on some versions of the Tablet, the bootleader cannot be unlocked? (ref: http://forum.xda-developers.com/z3-t...ction-t3091763 -- "Please note! It will only be possible to unlock the boot loader for certain releases of this model. You can check if it is possible to unlock the boot loader of your device by checking the service menu.")

If this is true, is there any way of telling when I am buying if I am getting an "unlockable" tablet?

The posts and guides I have been looking at are:

http://forum.xda-developers.com/z3-t...ction-t3091763
http://forum.xda-developers.com/z3-t...oader-t3017314
http://forum.xda-developers.com/z3-t...orial-t2980529
http://forum.xda-developers.com/z3-t...ry-qa-t3014211
http://forum.xda-developers.com/z3-t...gp621-t3013534

From what I've gathered, the steps are roughly as follows:

1) Put device in USB debugging mode and Install USB drivers (Fastboot for instance)
2) Place SuperSU on a SD Card
3) Install Dual Receovery "TabZ3C-lockeddualrecovery[VERSION]-RELEASE.installer.zip" as pr: http://forum.xda-developers.com/z3-t...ry-qa-t3014211
4) TA Backup as pr: http://forum.xda-developers.com/z3-t...ction-t3091763
5) Unlock Bootloader, also as pr: http://forum.xda-developers.com/z3-t...ction-t3091763
6) Flash " TabZ3C-lockeddualrecovery[VERSION]-RELEASE.flashable.zip" as pr: http://forum.xda-developers.com/z3-t...ry-qa-t3014211. I am a very unsure about this step, it says "Be sure to flash TabZ3C-lockeddualrecovery[VERSION]-RELEASE.flashable.zip from http://nut.xperia-files.com after installing the ROM and before you reboot, this way you will not lose recovery!". What does this mean?
7) Boot into recovery and install CM and GA (and SuperSU again?)

I apologize for being thick, but there is a lot of cross linking in these treads and some are 100+ pages long, so if there is important details hidden, spotting this is difficult.

Thanks for any help!