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There are three dihedral braces. They are all different.
Is the one with the most angle for a 3 channel set up?
Not as much angle.... Full wing with ailerons?
Straight brace for a clipped wing with ailerons?
That seems logical but thought I'd ask before I'd ask before I put the glue to it.
There are also a set of what look like dihedral braces but they are only 1.5 inches long. Where do they go or are they not for this plane?

short answer, yes. Longer answer (just my opinion, based upon my experience with a different WN kit), the low dihedral brace will give you a relaxing and well behaved four-channel flyer. The zero dihedral brace will improve aerobatics by, among other things, making it easier to maintain inverted flight. You can use either low or no dihedral brace with full or clipped wing. Clipped wing will, of course, perform aerobatics better.

the 1.5" pieces, if they are roughly .25" wide, are most likely the servo mounting rails for use in the fuselage. There shouldn't be any pieces in the kit that are "not for this plane"

They are not the servo mounts. They are about 1/8 wide. They look like the braces that go on a polyhedral to attach the wing tip pieces.
There are 6 of these. Two straight. Two with a bit of angle and two with more angle. I'm thinking they have to be leading and trailing edge dihedral supports.
I can't seem to find a way to post a picture or I would do it.

I found the smaller pieces that look like dihedral braces. That is exactly what they are. I watched the build videos again and the wing in the video has a space cut into the leading and trailing edge for them. My wind does not have those cuts. That is why I couldn't figure out where they went. They are spare parts.