A Molex plug is specified to handle less than 150w passing through it, and a typical cable has 3-4 of these, with the plug closest to the psu end of the cable having the full load connected on the cable passing through it.
Theoretically possible if you connect a single molex plug each from two different cables (and have nothing ele connected to them) to the molex to pcie connector.

But, the molex to pcie connector like the one you linked above have poor construction and below gague wires and are very likely to melt/burn under a sustained load of over 80w.