[Q] Custom ROMs on NK1 topic

Hey everyone! I've been digging through the forums trying to find an answer on what I can do with an NK1 without bricking my phone. I rooted using TowelRoot and would like to put in a custom ROM. (Hyperdrive in my case). I also looked into doing the 5.0 Lollipop through the guides posted on Galaxys4root.com, but I am unsure whether I can crack through the bootloader. I'm really new to all the specifics of these systems and trying to crawl through understanding the coding processes and layers. Thanks ahead to all you responders!