Help with what to look for in a 4ct plus Emerald cut or Oval cut diamond

[DiamondBaby]

Hi,
Having always gone up to now with round brilliant cuts for everything, I am thinking of something a little different for the next project. While I am happy enough picking the round brilliant, I don’t have a clue where to start with the emerald or oval cuts.
Size: minimum 4ct, really probably will end up being more.
Colour: D, has to be D. I don’t like colour, so that is where I am happiest.
Metal: everything I have is white gold or platinum, I am reluctant to go away from that. I have never really worn yellow gold at all
Clarity: VVS1 minimum, I really dont want to see anything in the Diamond, and I find I do, so start is there. Unless it is well hidden.

So I am looking for help as to where to start looking, and what to look for, and what are the big no no’s with those cuts.
I have a Jeweller who has been great, but I like to start the Diamond sourcing process before I talk to him, we then finish it together!

I’ll come back to the setting later, unless it really al has to be done together. But I think the size will dictate the setting.

Any help will be appreciated!
Thank you all!