I'll assume you are asking about puck shape LED lights. Those typically have a slightly focused output compared to other lamping so I'd say they need to be spaced a little closer than normal. But that is offset by the greater than normal distance from countertop to underside of upper cabinets; the greater the distance the beam travels, the larger the cone of light expands. However, LED lights, which I do love, have a lower lumen output. Pucks generally put out 200 lumens which is the rough equivalent of a 25w incandescent. So you may need more of them to give you the cumulative lumens needed for task lighting. Lighting layouts are tricky and always site specific. So with my lack of knowledge of you cabinet run and needs, take this with a grain of salt. I would space them 18" and antipicipate using more than initially planned. Phew!!! After all that, I much prefer STRIP style LED lighting for under cabinet lighting. There operate on 12v or 24v transformers, can be dimmed with a electronic dimmer switch and their lumen output is based on a linear foot measurement of the strip. 24v systems are better as they put out around 240 lumens per linear foot. The main advantage of these is the even output of light across the space. These are awesome when you're doing a whole kitchen because each short stretch can be daisy chained so they are all on one circuit. If you're doing one small area, stay with pucks. Hope this helps.

If you can access your home, take some colour samples in shades you like with you and check the light and aspect of each room, that can change colours, some rooms may be a little dull and need bright or cheering colours others may be hot and need cooling colours. It is very important you consider this before you start. Then choose ideas and colours you like and that suit your room, and then go shopping to see what is on the market and available. It is no use getting your mind set on a colour for example and then finding you can't get a fabric in that shade. Flooring will most likely be common to all rooms so you have to ensure the flooring you choose will work with all your planned colour schemes in each room. Check out all your options and things will then start to come together for you. When shopping pick up as many swatches and samples as you can, even take photos of ideas if you are able, it will all help. Most important thing is to take it slowly. Don't try to have it all done at once. Aim to choose your floor coverings, then have all your rooms painted, and floor coverings laid before you move in. Furniture and furnishings can be added at any time afterwards.

I love dark shades but from my experience oil stains on a dark shaded cabinets in kitchen specifically are more prominent.

the more gap you have the more light will diffuse. the beauty of cove lights comes from that gradient. if you have a small space then that look won't come. additionally, refering to your previous post, it will also be a place for pests. If you want this design, I would suggest you go with an LED and cover the gap with an acrylic cut out. that will give a nice effect. or create two levels, let the flat part stay where it is and make the circular one a recess