ddr3 is newer tech, and this mobo will have compatibility with future cpus because it is am3, whereas the other mobo before was am2+ and there will be no more cpus made for that socket. up to you.
the case should come with enough screws.
for a wireless connection, you can use either but i dont really know if ones better than the other. if youre looking at two specific products, you could search for reviews on each.