I have young kids, so I have worn VCA with both a small chest and a huge one! I think the 20 motif can work for both (for shorter folks, like me, it is not just the bust size but also how robust your shoulders are that influence how it hangs). Some people with a larger bust find that the 20 motif goes in the valley between the cleavage. I personally do not have that problem, but I definitely do with the magic pendant, and it is not a good look! So adding one more consideration to check for. I go back and forth with 20s, for awhile I only wore 10+5 (still my favorite length), then I only wanted to wear 20s, then I started wearing more simple clothing and easy-breezy more recently and I am back to 10+5. I think there is a place for either. For stones, I would go with MOP from your preferences, budget, availability and considering that it is classic and the most versatile of the options fitting your other criteria. I would also try Tigers Eye if it suits your coloring. It is one of the historical classic 20 motifs from VCA (you can see Grace Kelly wearing it). I personally love Onyx the most out of the most versatile and classic 20s, but I live in a climate that does not have sunny summers, and light and pale summer clothing is harder to pair with a 20 motif in onyx (though to be honest, I don’t love a relatively heavy 20 motif if it is hot and sticky out anyway).