Board PCI-E slot has a max supply of 75W but never is needed that much. GPU card manufacturers keep PCI-E slot power draw usually somewhere between 40~50W (if not less than that), I guess to avoid board damage, or even board heat soaking. Because all this power power must run through the board's circuits. Some older SLI/Crossfire-capable boards even had an extra power connector right next to PCI-E slots to aid. Others, even derive some power from the 4/8-pin CPU ATX power connectors.
TDP = Thermal Design Power
TGP = Total GPU Power
TBP = Total Board Power
Only TBP is what the entire card draws.
TGP is only for the GPU without memory modules, fans, leds or anything alse.
TDP is a very questionable value. Its usually how every manufacturer is interpret it. As the name implies is about heat. Some manufacturers are naming this equal to TGP, as all the power of GPU traslates into heat which is correct of course, but others they mean only the GPU heat that is "moving" towards the cooler under specific circumstances, which of course is less than TGP as some heat is also dissipates through the PCB and the back of the card.
The same thing is happening with CPU TDP as AMD and Intel are using it differently.
Also, lately there is a new power value called PPT(Package Power Tracking) and at least for AMD CPUs and GPUs is representing the entire chip package. Its equal to TGP for GPU.
The nVidia reference RTX3080 (FE) has a TBP of 320W, but most custom cards have a little more than that depending the model.
