Typical graphic card draws power from PCIe slot (up to 75W) and the rest is taken from auxiliary 6 or 8 pin connectors (PEG). I have a
non-conforming motherboard that says "25W max" on PCIe slot, hence I'm looking for a card that takes close to 100% of its power draw from the PEG(s).
Please note that I'm NOT looking for a card with 25W total power. Total power is not limited, only the balance between PCIe and PEG. A GTX1070 at best.
I know about powered riser, I consider using it as a fallback option in case such card doesn't exist.
Description of my system for those who are curious: It's a Thin-mini-ITX and as such it's not supposed to support any graphic card. Board is Gigabyte GA-H81TN. As Thin specs call for, this board is powered by external 19V supply and all the ATX voltages required by PCIe slot are derived by onboard regulator. The 25W limit is the limit of this regulator which is part of the board and not replaceable. I also have 200W Dell DA-2 12V/18A brick to provide 12V to the card via PEG, similarly to external gpu via thunderbolt hack. I know that with only 4 lanes the performance won't be stellar, and the very point of a Thin system is to be very small - but I want to give it a try just for kicks. There is no chasis, as it's just one board so it sits on the desk on an insulating mat, which means that there are really no limits on the card except from PCIe power draw.
/edit: As I've just learned, the PCIe power limit is tied to card length. Cards shorter than 16x are not supposed to ever draw more than 25W. The slot is open-ended but it's a 4x slot nevertheless so the power limit is something to be actually expected.