there is no perfect dimensions for an island. Try to organce space subdividing into smaller cabinets of 60x60 cms which is the max space for a structural division and works for seating area as well

Totally doable as long as the island is not too bulky. And of course if the circulation space around the island is at least 3'-0" wide. You don't need too much space to move around in a kitchen because you should be able to pick up a hot dish and put it down on another surface without having to move too much. 12'x14' is a large size and a work island would possibly make the space more practical to use. In the pictures attached, the work island is only 2' wide but 4' feet long

I wanted to use a shimmery pearl backsplash but it was problematic to install. Looking for something reflective. My island is deep blue (sea serpent by Sherwin-Williams), cabinets white with clear glass in second row uppers, fixtures, pulls and knobs all champagne bronze. Hoped to find something more exciting than white subway but I need help and fast so we can install the range hood and the stove!

I have used both with good results. The main difference between Quartz and Granite are 1) price, 2) colour range. Granite generally works out cheaper, because you can buy the exact quantity you require. Quartz comes in large slabs of specific sizes- standard size being roughly 10'-0" x 4'6", so there tends to be more wastage if you don't plan the cutting well. But Quartz is pretty and comes in a wide range of colours and can be re-buffed at a later date. Quartz also comes in various thicknesses- the most commonly used being .75" to about 1.25". And especially when you use dark wood cabinets in a kitchen or bathroom, beige and white counter tops work very well. Some people go even with coloured counter tops like blue, orange, yellow. Natural stone in light colours tend to be porous and stain easily, so I prefer to go with pure black which is safe.