In terms of choosing your brick slips, there's no need to match your house bricks, choose something that fits with your style and your kitchen. As a natural clay product, most blends of brick slip will go with most kitchens.
You can combine the slips with an upstand - the closer in depth they are the better, brick slips are around 22mm but including adhesive will protrude 25mm or so from the wall in total
We recommend using brick slip sealant to stop things soaking in and making cleaning that little bit easier. If you're doing a separate feature wall, it's not needed.