Originally Posted by uoY_redruM
What exactly does this do? Update everything that you would normally only be able to update via the RUU file?
Say for instance the new T-Mobile update. Updated via the flashable zip someone provided. Already have root and custom recovery. That doesn't provide updated radio, hboot, etc (if I understand correctly) and that's what this does?
The answers to your questions can actually be found just doing a few searches within the thread, but I will answer it one more time. Firmware does not contain system image at all and does not touch system at all. Your Android system is considered software. Software is never included in firmware packages.
Firmware is device controlling and device specific code and data. It is what allows your hardware to run. It is generally speaking unrelated to software, with the exception of boot.img, which does specifically correspond to the software you are running.
Any of the custom firmware packages in this thread can be modified to your liking. If you want the stock recovery then keep the stock recovery. If you don't, then remove the recovery image from the package.
If all you're looking to do is update the firmware that was recently updated via the OTA simply flash the small custom firmware package. It contains every firmware image that was updated minus the recovery and boot.img.
You need to understand my advice to users to stay away from this thread until you have a solid understanding of what firmware is, is for users own safety. You can very easily hard brick your device (rendering it's completely dead and about as useful as a paper weight) incorrectly modifying or flashing firmware. You really cannot hard brick your device flashing an incorrect custom system (eg a custom ROM). That is a misconception an important point to make.