Looking forward to see the results! All is still experimental so you're bound to find some bugs and instruction typos, that's what you guys are here to help with.
The remote sense inputs are for displaying a more accurate output voltage on the power card. By default the output voltage is measured at the designated contact points at the front of the card, but because of the high current flowing through the wires to the GPU the actual input voltage will be difference because of droop during load. The most accurate reading will be from the decoupling capacitors (MLCC) at the back of the GPU, so just solder a wire from the positive remote sense input to the positive (GPU Voltage) side of the capacitor and the negative input to the negative side (Ground). If there's a voltage on this input it will automatically be used for reporting rather than the on-board sense.
The Hotwire connectors (six in total, three at the top and three at the bottom) are supposed to help you adjust the voltage of auxillary VRMs (think on-board memory and PLL). Hotwire channels 1 & 4 come with increased ranges and each step causes a bigger change, typically suited for a GPU VRM or similar. In the end which channel will fit best depends on the specific VRM design and the resistor values used in its feedback loop. One step could be just a few millivolts on one design and several hundreds on another. I'd say you should try with channel 2,3,5 or 6 first and if the change is too small switch to channel 1 or 4. I'll update the instructions with more clear information.