I'd stick with the same white. Black shutters will be beautiful but stay true black. For the stairs put treads on them like a bluestone or granite or even marble (slippery) and do a stone or brick veneer on the risers unless you choose marble. It will be less expensive than you think.

What a gorgeous home! Off-black may look faded, I'd stick with classic true black or a black/green like SW Black Emerald in a semi-gloss or even a gloss. A gloss sheen will hold up really well and add some impact.

My experience with china white is it often takes on a grayish dirty look.

I'd go with BM Super White and a true black shutter and glossy deep red front door.

The PAINT should precede the "white" or "black" color, as you are going for high contrast, spending much $$ and it should perform and last! Low lustre usually on body of house, satin on trim and shutters. Front door satin or semi. If you know what is standard, then you can choose, but you will need to see what sheens are offered in the best products. No more oils exterior, VOC regulations. SW white is grayer than BM white. Factory white paint was about high opacity, not color. That is what became "classic" about it. Do you have time to experiment with NUANCES of "white recipes" affected by large scale, outside reflected light, contrasts in setting, sheen levels,.. If not, talk to a paint professional at a store! Sherwin Williams' DURATION or Ben Moore's AURA Exterior line. The porch floor,is it gray? steps can be painted same color for flow, in proper porch and floor paint.