Use your EPS CPU 8 pin adapter if you need more PCIe connectors
That one will support the high wattage. Never use the SATA connector
even that is risky.
if your PSU doesnt have enough PCIe connectors it probably isnt well-suited to bitcoin mining.
almost any molex-pcie or even eps-pcie adapter is made with 18awg or thinner wires, and not suitable for the loads required by modern bitcoin mining hardware. they are designed for running low-end GPUs on systems that didnt even have a PCIe connection.
ie: they are built for <100W but bitcoin mining typically draws >150W