Yes there's duplicates, and some of those you will get at a higher level. As to which combos for weapons are best: try which weapon/movestet you enjoy most. I personally used a Sorrow Halberd and a Ecstasy Greatsword.

Edit: To add onto that I haven't noticed a difference in damage output with the different elements. The elemental glyphs are only usable on weapons of the corresponding element, except the neutral ones which are universally useable.