18K vs 22K White Gold and setting transparent rounded back cabs

Hello All, I am a beginning ring-maker who is making the rings for my
upcoming wedding. I have already bought the stone for my fiancee’s
ring. It is a 1C triple A emerald. It is transparent and is an
oval cabochon. It has a slightly rounded back, so I was wondering
how should I set this when I want to keep it a low bezel. Suggestions
I have received:

  1. Drill an oval shape in the band so that it sits in the oval
    evenly. Drawback: Transparent stone, will make it look darker with
    skin behind the stone.

  2. File a little bowl in the top of the ring so that the stone can
    sit in it. Drawback: Unlikely to get the bowl shape filed perfectly
    to have the stone sit flush.

  3. Use a thin piece of wire around the inside the bezel so that
    stone’s edges sit on the wire. Drawback: might be able to see the
    wire through the stone.

Please make suggestions and/or evaluate the above suggestions.

I have tried using 18K white gold and have found it hard to work
with. Does 18K white gold end up with a silver like finish? What about
22k White gold? Is 22K easier to work with and have a silvery
finish or is it more yellowy? Are there any downsides to 22k? Will
it ding more easily?

Any feedback would be greatly appreciated, because hopefully this
will be on her finger for 50+ years.

Thanks, Jason