Thank you, it's a .41 yellow gold DBTY. I loaned my bee to a cousin in a different country and I have yet to have it returned... so I've never had the opportunity to layer. However I do layer it with my Tiffany arrow. I currently have that combination on now with silver bead earrings.
Rose gold is my most preferred metal. But with Tiffany DBTY, their rose gold bezels are too thick to my liking. I normally always do platinum with diamonds to empathize the diamond, or do yellow gold if you want a softer look that blends with classic or vintage pieces. I think yellow gold would look great on you.
I'm petite although busty so I have to be careful with necklace lengths; I also have issues with bigger pieces not looking proper on me. However with Tiffany pieces, since they are designed to look delicate, it's easier to do bigger pieces. Long term go as big as you can because you will not out grow the stone. I already feel like the stone is too small for me but it is a great and very substantial size and works perfectly to layer. I shortened it to be a length that I can layer my other necklaces with. Stay under a half carat and you'll be fine I would think. If I can help in any other way please let me know.