Post [Q] New to Rooting/ROMs - Samsung Galaxy SII (Sprint/SPH-D710): JB Modem and ROMs ?'s

To start off, I have rooted my phone using the tutorial using the GB27 Jelly Bean kernal through Rwilco12's Android Forum

(Shout out to rwilco12 for the guide)

I am this far, and I have installed TWRP Manager from the Google Store.

I want to install ROMs, but I see a lot of threads and warnings about 'Don't use JB modem!!!!'

I would like to get a full understanding of not using JB modems, because I have 4.1.2 on my phone, and wonder if that is what they are referring to? And if so, what is an alternative OR what ROMs do not need JB modems?

Also, are there any extra steps in between rooting the phone and flashing a custom ROM, because I want to be sure that I have a way to recover in case of the infamous 'brick' shall occur, or something of that nature. Thanks.

Any advice/criticism/references is encouraged!