How do I connect my triple redundant power supply with two 20-pin ATX plugs into my 370DLE motherboard, which also have two 20-pin ATX connectors?
If your power supply does have two ATX connectors, then it's safe to use both on the motherboard. The two inputs and motherboard connectors are just in parallel to share the current load. Only one is needed, but if your power supply has this capability, then please use it.