I think your instincts about quantity are right on - 2 or 3 (depending on the height of the items to be displayed) feels right for the height of that space. You want to take a close look at the shelf images you posted and compare with your space. It's a little hard to tell without more images of your kitchen, but it looks like you have a "transitional" aesthetic, not quite modern but not quite traditional either. The shelf images you posted are both of very modern decor. The reason the long shelves look good is that they are very thick, and the reason the thick shelves look good is because the aesthetic is very modern. Floating shelves can certainly look good in a transitional setting, but they probably want to be thinner and therefore shorter. In addition, I would keep the layout symmetrical rather than staggered (again, staggered is more modern). Consider either a set of shelves of moderate length centered in the alcove or two sets of shorter shelves each centered over a pair of cabinet doors. If appropriate for the items you plan to display, you might also consider shallow picture ledges like the image below, rather than full depth shelves.

If you want to have a 3cm shelf around 5-6" deep to cap a stone backsplash, ask your fabricator if they can drill 1/2" dia. holes to accept hanger bolts. 3/8" x 6" hanger bolts can be screwed into studs, leave at least 3" protruding from the wall, alternatively you can use 3/8" x 7" lag screws, this might be easier to screw into the wall, and then grind the hex head off after in place. The stone installer will need to put epoxy in each hole to allow it to set around the support. Be sure the supports are perfectly level, and placed in the middle of the stone shelf.

ditto to KR. (I wish you would have tiled all the way up though) You have such a tall ceiling, that large expanse of wall if going to look bare. This one looks pretty good. I like the warm wood, the copper, the plant, and the multiple shelves. don't be afraid to mix in some mixed elements. with a white/gray kitchen, you need some of these warmer/organic tones to keep it from looking too sterile. I'd prob do a sconce or two (or even a pendant) See how this one looks? tried to find open shelving w/no tile and a higher ceiling. other visuals. schoolhouse style sconce. Here's one in the white shelves I notice you have a light in the ceiling. if you don't want to do the sconce, you could opt for a pendant shelves partial, with pendant, Schoolhouse style pendant shown here and fully across w/two sconces. just so you can see You could do a shade darker or lighter than your floor if you like the wood. I'd take them side to side. make sure to add some greenery to the decor. even some plants that spill over the edge. Don't forget the runner

Aloha @Floored You: TileDesigners Thank you for the questions. I was hoping it could be fastened with an adhesive vs the wood. Was hoping for feedback if that would be a good option. We had water damage to our kitchen so since we had to tear out the drywall, we thought we should try to make the kitchen how we’d like it to be. Electrical is where it was previously located. There were high cabinets before. This is a cookie cutter style house for this subdivision we are in. Cabinet height is 34 1/2”.