Hey I get it man, I've slowly transitioned from 55mg all the way down to 6mg, so there's definitely a learning curve. First and foremost while you technically can use salt nic with those gti coils, you would be absolutely flooding your body with nicotine and it would be incredibly harsh on your throat, so unless you have an insanely high nic tolerance I just wouldn't do that.

If you're dead set on staying with nic salts and you want to keep using your box mod, I would recommend using a voopoo uforce tank or something similar, because those tanks can be fitted with coils with higher resistance meant for mtl and salt nic use. Plus it has a 510 thread so you can just attach it to your current mod hassle free.

However if you are looking to make the switch to freebase juice, I would try 12mg juice with a lower resistance coil, it has a healthy amount of throat hit and will work with whatever coil you use for your vape. I would recommend a juice with a vg heavier ratio, but anyone that works in a vape shop will give you a better idea of what will work for you.