Question [Q] Modem update and AOSP Roms [ELI5] [CM11]

This is a multi part question and I am hoping to have a bit of light shined on this topic for me.

Please feel free to explain it as if I am 5 and thank you in advance for your assistance.
Currently I am on the CM11 nightly builds and and loving them so far. Recently Sprint has turned on a lot of LTE towers in my area and these are the questions I have:
  1. Is it common practice to flash back to a TouchWiz Rom and update to the latest modem then update profile? If yes, what is the benefit to this?
  2. Can I just update the modem though Odin while remaining on my AOSP Rom? Is there a downside to this?
  3. Should I update BOOTLOADER, MODEM, RPM, AND TZ as well? Example: http://forum.xda-developers.com/show....php?t=2357171
  4. Is there a TAR (similar to the link above) for the recently released MJA?
CM11 Rom: http://forum.xda-developers.com/show....php?t=2529727
Thread I am referring to: http://forum.xda-developers.com/show....php?t=2338919

Most of these questions stem from my Epic Touch 4G days were this was all needed.

Again, thank you in advance.

- Dan