Most SATA hard disk drives do not use the 3.3v power (orange wire). From my reading, only newer 1.8" SSD drives use the 3.3v. And now the new SATA specification uses the 3.3v line as a power saving control option to shut the drive off, so in that case you would not even want it connected. You should be good with the 2 relay board setup. However, if you really want to be certain that you are dropping all power from the drive, here is a 4 relay board setup for that.
This shows how to wire a 4 relay board for a SATA power cable. The yellow wire (+12v) has to be tapped into to get power for the relay board. Make sure to get the power from the supply side of the extension cable, or you will end up with a bad chattering relay condition! Also, one of the black wires must be tapped into. Even though the ground wires should technically be the same, it is recommended to use the one next to the yellow wire, as that is supposed to be the ground for the 12v. I cut it and stripped both ends and put them in the DC- terminal connection. The extra yellow wire that goes to the 12 DC+ terminal came from a spool of wire that I have. You can use a piece of wire from something else as long as it is about the same wire gauge.