First I'm glad you're going without the raised island. I have the raised island now, and honestly, as I get older, it's getting harder and harder to get up on those bar stools. LOL. Your layout now is very similar to mine with the exception that for me the fridge is across from the sink. Honestly? I find that there isn't enough room at the sink for prepping so I'm washing, having to bring it to the cooktop counters to prep and then bringing it back to the sink to get rid of the excess. I think naf naf's kitchen layout is a lot more functional. If that doesn't quite work because you want the fridge near the dining room, what about switching the sink area and the range? Like below. This will keep your island for eating, sitting at, etc and no dirty dishes. If your DH prefers to look out while cooking, you could put a small prep sink and trash drawer on the island, keep the sink and DW just for cleanup and secondary prep space and the range where it is with plenty of room on either side to spread out. I would end the wall at the end of the island counter and I do like the cookbook shelves.

Is this the exact spot where the mirror will be hung? I'm only asking because looks like your current vanity is on the opposite wall and I want to make sure that the space you'll have for the sconces will be the same.

OH.. LOL The one that is in the center of the 3/4 can easily be made a picture light, or you can cap the electrical and put a plate over the outlet and just hang art over that spot in the wall. the other two you can do fun deco style sconces with that blend into your theme or even only use one or none, they can all be capped, not gone, but capped and you can then place art that is off-center now, centered. https://www.lowes.com/pd/Portfolio-Round-Metal-Electrical-Box-Cover/3659600?cm_mmc=shp--c--prd--lit--google--lia--183--ceilingfanaccess--3659600-_-0&store_code=1753&placeholder=null&gclid=EAIaIQobChMIjJ3xj6PT6gIVEgnnCh2lgQt8EAQYAiABEgL89vD_BwE&gclsrc=aw.ds

The important distance to consider is the distance between the center of the vanity to the center of one sink. That distance never changes regardless of the size of the mirror. The wider the mirror, the less distance you have between the sconce and the mirror. If my calculation is right based on the measurements you gave, that distance is 21" (please confirm it as I don't explicitly see it on the measurements you gave us). The distance between the edge of the sconce and the edge of the 24" mirror is 6.25". This number came from that calculation: 21" -2.75" (half the width of the sconce) - 12 (half the width of a 24" wide mirror) = 6.25". Now if you use a 36" mirror, the distance between the edge of the sconce to the edge of the mirror would be .25" ( 21" - 2.75 - 18"). You don't want a quarter in. wall between the sconce and the mirror. If you were to find a 28" wide mirror, that distance would be 4.25" ( 21" - 2.75 - 14"). I think the width of the sconce is more in proportion with a 24" mirror. I also think a 24" mirror looks nicer with a 27.5 wide cabinet below it.