help : cwm to twrp + guidance

Hi everyone,
as I just got a new Z3 compact after a while with a company iphone, i wanted to get rid of all bloatware and use a stock rom right away. I have had some previous experience with android rooting/flashing but this was a while ago and I must admit I may be a bit more out of depth than i thought.

I figured I needed to root first, to be able to get a recovery mode working, to be able to flash new roms (or so I think is the way to go).

Forum posts led me to this method which I sucessfully did.
Also it seemed from this post that downgrading firmware was essential.

My Z3C now runs 4.4 1285-6521_23.0.1.2.105, and I have access to CWM 6.0.4.7

But now, I realise that most roms (or at least the 6.0.1 stock SLiMM which I think I want?) actually require TWRP - and fails to install with CWM (zip install finishes in a few seconds - with no changes).

I've tried to install TWRP manager from the play store and install it from there but the install yields an error. I guess because of CWM presence? The files for a flashing it manually are missing from their official website.
I've looked around for tutorials on how to install TWRP over CWM but couldn't find a clear way.

So I'm wondering what are my next steps.

Should I install another kernel to be able to run TWRP, like this one?
But do I have to flash the corresponding firmware first?
And should I use the Advanced_Stock_Kernel_Z3C_MM_6.0.1_23.5.A.0.570 download if my phone needs 23.5.A.0.575 - Unbranded - CE1 [Central Europe] (1288-7915) (I'm in France)??

Lastly, will I need to restore the DRM keys and at which point?

You might have noticed I'm confused now ⁀⊙﹏☉⁀
Any help is appreciated ! (> ^_^ )>
Thanks !

Guidance Undoing some radio modifications

Hi all,

I've got a Verizon Galaxy S5 that's been modified to behave like a 3G phone -- 4G/LTE is disabled and the ESN has been swapped with another phone that I have (disassembled) in my possession. I've used it this way for a year or so, but my carrier (Selectel) supports 4G now, and I am looking to undo the modification. The person who made this change for me can't be reached, and I can't remember the name of the software I need to do the job.
Can anyone point me in the right direction?
(I've rooted/flashed/etc. extensively and I program computers for a living, so actually doing this shouldn't be an issue once I have the tools, but my memory is failing me.)

Thank you.

Voice guidance muted when music playing

Hi folks,
Have Android auto on pioneer next 8000. F70 dab European model. Works great but recently when playing music from play music or Spotify voice guidance from maps isn't working. Instead of voice music mutes but no instruction is read out. With music stopped voice guidance works perfect. I could swear I changed some setting recently which said mute music during voice guidance but can't find any more.. Phone is htc 10
Thanks
Mick