[Sprint HTC One (M7)] ianthomas:
I forgot to thank you for your advise, which I took, and I don't regret :) There is a tiny little fine print about this though: " you don't have to relock the bootloader to flash an RUU"... That is not mentioned in the guides I read, and I will try to clarify in my noob post.

It is confusing for me too, but one of my theories was right, and I felt like a dunce once I figured it out, and I think you figured it out too...

Anyways, the HTC one will be for my brother, so I had limited access to it, and finally did more tests on it to figure things out.

I will try and answer your questions to my best of knowledge, but please keep in mind this is a noob/guinea pig point of view that is still asking questions, and I may be wrong on some things, so bear with me, but this has worked for me:

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Being on a Sprint HTC ONE with Hboot 1.56, originally on stock 4.06.651.4 , and S-OFF thanks to Firewater (other methods failed for me). I would recommend getting S-OFF now (to whoever else this may help).

OK v1ral, as far as I know, the ability to flash the 4.06.651.4 RUU WITHOUT having to relock the bootloader is from WITHIN the stock ROM itself, NOT from fastboot or anywhere else.

TIP: When unlocking the bootloader, simply save the .BIN file HTCDEV sends you, and save the command used to unlock for quick unlocking and relocking, just in case.

However you have to flash stock recovery first if s-on, how about with s-off?

You don't have to flash a stock recovery, because the RUU itself does that for you, regardless of S-ON or S-OFF. The only condition is having to relock the bootloader if S-ON BEFORE running the 4.06.651.4 RUU from WITHIN the stock ROM you're in, but obviously that is not necessary if S-OFF.

Can I RUU without relocking bootloader with s-off?

As far as I know, yes. that is the perk of having S-OFF.

Can I install an ota update without flashing stock recovery with s-off?

As far as I know (please correct me), the RUU itself flashes a stock recovery anyways, or at least that's one of the messages it gives while working. Keep reading for the info on how to install the OTA properly in my case.

Last thing, what are the steps to update my stock Rom, while being s-off?

OK, here we go, there is a very important, and easy missing detail nobody mentions in the guides I read, and the reason I was soft bricking with any rom.

How to OTA update from 4.06.651.4 to 4.06.651.9 properly, regardless of being S-ON, or S-OFF, and avoid bootloader bootloop for noobs

First off, If you're already in trouble, and can't install a stock rom, in a bootloop, or don't know how to adb sideload a rom into your device, etc... PM me to try and help you out of it, and start off in a stock room. That may take more time.

Moving on, assuming you're already in a stock rom, or any 'working' rom for that matter, meet these requierements first:

Make sure you never installed HTC Sync before, EVER. Have proper drivers installed, and a correct ADB online connection to your phone is important. I'm just assuming you didn't lazy out, and know how to research the drivers in here already. I just need you to run the command

and get a correct online connection between your phone, and PC. Another thing is not to use usb 3.0, or the frontal usb inputs on your PC, and use the back inputs just in case...

And even MORE important tip, is to never... EVER... use cheap low quality or damaged usb cables. I learned this the hard way hard bricking 2 phones in my old LG LGNPST days (LGNPST is another type of flashing tool for LG devices).

Having a damaged usb cable may be really dangerous, specially if your'e S-OFF

Having an al in one folder with the tools to work is pretty convenient, and user BD619 gathered one in his thread

He may not always have the latest version of the TWRP or CWM/PhilzTouch recoveries in it, but you can easily get them in this forum obviously.

TIP: TWRP is the recommended recovery on this device, version 2.7.0.3 didn't work for me, but the new 2.7.0.4 seems better for me, but I still can't mount an OTG drive to it, so you may have to learn how to push/adb sideload ROMs or files into it like this.

OK, from WITHIN your stock ROM, run this 4.06.651.4 RUU first (you only need to relock bootloader prior to running it if you're S-ON):

http://xdaforums.com/showthread.php?t=2658910

It doesn't matter if you're already on firmware 4.06.651.4, run it anyways (it will flash a stock recovery, and more), reboot, and

THEN relock your bootloader, regardless of being S-ON or S-OFF

That was the little detail I was missing, and should've figured out before...

After relocking the bootloader, reboot back in, and THEN, and only then, you can download and install the 4.06.651.9 update from within the Software Update option.

After updating properly to 4.06.651.9, it is then that you can unlock the bootloader back again, flash TWRP, and root with it, or get ROMS already rooted without hiccups.

Finally, if I'm wrong on any of the small details in this, please correct me, but it was what worked for me at least.