I am with the few that don't like them to be painted. I've seen too many that were sloppily done, and/or obviously had many coats of paint applied over the years. Painted ones tend to be more difficult to dust, because the paint used is usually the eggshell or flat wall paint, not glossy in the same color as the wall. However, since yours are already painted, I would say keep, or paint, them the color of the wall and not change them to white. Painting them white now serves no purpose.

I suspect the paneling above that appears to be on an angle, is a bulk head for something, and I would be very cautious, trying to remove it. It may hold plumbing pipes, or it may hold ac vent pipes, etc. I would paint the walls all to match, but, leave the wood on the slanted ceiling part. I would paint the bookcases white too (different sheen, but, same color white as the walls), but leave the mantle like it is.

furniture on natural oak hardwood floors

To really keep it light, use the same color on the walls. This is pretty yellow for a trim color so stick with warm colors. Greens will work better than blues if you want some color. Since you say your house is open plan, what colors do you already have in the rooms the kitchen is open to? Can you post a picture or even a couple so we can see what you're working with?