The sr and lr are ohms. The sr have higher ohms like 2.8 to 3.2. I forget the resistance on the lr but it will be around 2 ohms.
For a kgo I would recommend a 1.7 single coil or 1.5 dual coil carto. Your
vape will be much, much better. There is not enough power in the kgo to push an sr carto. I use sr's on variable voltage anywhere from 4.8 to 5.6 volts. I just put one on at 3.7 volts and it was just what you described, sucking air.