Plumbing of main drains and skimmers

What is the "preferred" method of plumbing main drains and skimmers? Assume two main drains and two skimmers.

1) Main drain #1 plumbed to skimmer #1, which is subsequently plumbed back to pump suction. Same arrangement with set #2.

2) Main drains plumbed together and plumbed back to pump suction. Skimmers plumbed together and plumbed back to pump suction.

The pool will be equipped with an auto fill system, if that makes a difference.

Also, how many separate return (pump suction) lines should be run back to the equipment pad?

Thanks ever so much.

Mine is plumbed as 3 suction lines (from pool). Two main drains tied to one line, each skimmer on separate line. Two returns (one in deep end, one in shallow). Should have added a return at the stairs to help keep them clean. The advantage of separate skimmer plumbing is that you can better control the suction when vacumming (which I almost never do now thanks to a Pool Rover and Pool Buster).

The returns are the pressure side of the pump, the main drain/skimmers are the suction side of the pump.