A: Yes they are angled from one end to the other. In other words, they are cut on a straight line from the smaller end to the widest part on the other end of the shim.
A: If visible piece, you'll prefer to make a shim out of same wood. If this is for inside (not exposed) shim, it will probable work great. The last ones I got were hardwood about 1.25" wide and 1/4" high at thickest, but the lots available may vary.