Are there any "powerless" (draw power from mobo only, not psu) GPUs that are worth mining with?
Any reason why you don't want to consider cards that require supplementary 6 or 8 pin power? I would think most limitations (such as the lack of the necessary connectors or other PSU-related constraints) could be solved easily.
I was looking through mining hardware on Amazon and saw a pic in someone's review of a mining rig that had 6 or 8 cards with no PSU connectors. There was a stack of boxes in the pic with AMD RX GPUs but I couldn't see the model due to the size of the pic. There was just something about the simplicity of the rig that appealed to me and wanted to figure out what he was using.
Of course you are correct regarding the supplementary power connectors. I just figured maybe the GPUs that don't require them may be more efficient and less expensive. Figured there was something I was missing going on there.