Is it ok to connect powered risers directly with the molex? I have a 5 non ref RX 470, all with 8 pin connectors.
Yes that is the best way. Although you may not want to connect more than 2 gpus per molex chain. 3 may be okay but I am not certain
For the non ref 470, if it has 8 pin PCIE connector, you can connect up to 3, otherwise, it is safe to just connect 2.