Soft-Bricked Samsung Galaxy S5 - "Set Warranty Bit: Kernel" I recently did some stuff to my Samsung Galaxy S5 UK (SM-G900F) on Three and Marshmallow 6.0.1:
(In order)


Successfully install TWRP using Odin
Successfully root using Chainfire's Systemless Root
The message 'Set Warranty Bit: Kernel' starts appearing on the Samsung Android logo during boot, but it still works fine. (I think this means I voided my warranty.)
Successfuly install BusyBox using this app
Install XPosed Framework ArmV7 version, following a guide I can't find any more, but I got my file from the official XDA thread


Now when I rebooted my phone after installing XPosed, it gets stuck on the Samsung Android logo with the 'Set Warranty Bit: kernel' message. I can get to TWRP by (steps, not methods):


Removing and replacing the battery
Plugging in the charger
When the battery charging animation shows, pressing Home+Power+VolUp


What I would like to know is:


Should I restore it using Odin?
If so, with a Stock or Custom ROM?
If not, how is it recoverable?
Samsung phones require a special version of Xposed -  the regular one just won't work as you experienced.

Since you can still get into TWRP, the situation is still under control. Uninstall the current one with the uninstaller from the official Xposed thread, try booting up, and if it returns to normal, download and install the special version.