Salts are easier on your throat.. Both myself and DH have throat problems from smoking for decades, so salts were a godsend for both of us. He couldn't have picked up vaping at all if it weren't for the salts.
So you will want to try some salts if the nicotine in freebase form is too harsh on your throat. Otherwise, I see no need. Vaping salts and freebase side by side I see no difference outside of throat hit.
You can always pick some up in your current concentration and try them, decide for yourself. If you like throat hit though you might not like it unless your going into the high concentrations, which you likely wont need to do in that Z-Biip..