This discrepancy should have been caught when the countertop guys templated the countertop. Are your walls that messed up, or is it because of a flawed cabinet installation? Regardless, a 1/2" gap is ridiculous. You can have a new top properly fitted. Bingo, problem solved. Is there a backsplash to be installed? That can hide a gap, with the exception of the gap at the end of the countertop. Depends on if that edge will be visible or not. Everything else is a compromise of sorts in that you can reduce the gap in the back but you overhang in front. You can slide it back but then your cabinet overhang at the front of the cabinets will be skewed. You can scribe the countertop as is, slide the entire thing back 1/2" to close the gap on the right. That'll give you even reveal on the front overhang, but it'll be 1/2" less front cabinet overhang than you have now. Or you can do a fraction of that 1/2". Slide it back 1/4" for a 1/4" gap on the back left, and lose 1/4" of overhang at the front of the cabinets. You can notch the drywall on the back right wall and slide the top back. Same effect as the previous recommendation, but you're notching the drywall instead of scribing the countertop. Another alternative is to use mud to float out the back wall. Essentially you're making the back wall "thicker" to bring the wall forward to meet the countertop. It'd have to be done in several steps, and you'd have to feather the half-inch thickness down over the run of the wall. But that also depends on windows on the wall and how the existing window trim will be affected. There are fixes and there are band-aid repairs. Mongo

I don't know what you intend to do regarding backsplash height (that's the distance b/w the finished counter and the bottom of the upper cabinet and light rail), but here's what I usually tell people when they're considering the height for their backsplash. The standard is 18"...regardless of the reasons why, it's still the standard.. How this affects your kitchen.... Refrigerator and other tall cabinet heights...Because wall cabinets are meant to be mounted at a standard height, cabinet manufacturers take this into account when designing tall cabinets. Tall cabinets are designed to be the same height as the installed wall cabinets so the tops all line up. When you change the height a wall cabinet is installed at, it affects cabinet top alignments. With the refrigerator you can usually mount the upper cabinet a little lower OR order a shorter upper cabinet, but be sure you don't make the alcove any shorter than 72" tall b/c newer refrigerators are 70" to 72" tall (and seem to get taller each year!) With other tall cabinets like oven cabinets and pantry cabinets, they're a standard height and designed so they're the same height as the wall cabinets when those wall cabinets are installed 18" above a 36" high counter. If you have custom cabinets, this may not be an issue b/c your cabinetmaker can adjust the cabinet heights. But, if you are using stock or even some semi-custom cabinets, you cannot change the height. You can often get taller cabinets for use w/36" or 42" tall wall cabinets, but not shorter for 30" mounted lower. But, even those that are taller are also adjusted based on standard wall cabinet heights + an 18" backsplash height. Small appliance height...Small appliance manufacturers often design their products to meet this 18" standard...for example, my KA stand mixer (bowl lift) is around 17" and many coffeemakers and blenders are just short of 18". So, you need to be sure you have room under the cabinets + light rail to fit those appliances. Small appliances... Keep in mind that if you're using an appliance on your counter, you must be sure you have room under the base cabinets to move that appliance around easily. Don't, for example, tell yourself you're only going to use it in front of your upper cabinets so you don't need to worry about its fit. In reality, you will be moving things around on your counter while you work and most likely your appliance will be moved under the cabinets at some point. You don't want to tear your light rail off or damage it (or the cabinets). Also remember that "standard" upper cabinets are 12" deep + 1" for the door...so they stick out 13" over your counter...leaving you only 12" or so of workspace in front of the upper cabinets...not much room to work in by itself! (If you have deeper upper cabinets...say 15", there's even less counter frontage in front of your upper cabinets...3" less, so 9".) Vertical workspace... Another consideration is vertical work...

One advantage to having it seamed the full depth of the counter is they can use a seam setter to electronically pull the slabs together and give you a very tight seam. I don't know if you've seen my seam that I've posted a few times, but it's a hair's width. I can barely feel mine and can't see it unless I'm standing nearby. With a solid quartz like yours, the particles are like fine sand, so the cut should be very smooth.

In terms of overall length, I have from left to right: 48" Freezer(18")/Fridge(30") 3/4 inch side cover panel 120" counter top, therein 36" induction cook top 3/4 inch side cover panel 30" wall ovens 48" pantry (2x24" high cabinets) 2" cover panel to the wall = 249.5" Total I've been going back and forth on the hood. It's probably the most discussed item. Originally we planned to get a custom hood liner built for an insert hood, but now we are leaning towards this very basic BOSCH pull out hood. Minimum mounting clearance over cooktop is 25 3/5". There is no maximum clearance given in the spec sheets. It should come in right around 30-32" clearance (math: 84" tall cab (incl. toe kick) - 36" base cabinets - 15" wall cab to mount the hood to - 2" for the hood hardware = 31"), which is very average as far as I can tell. I was planning to build a custom open cabinet left and right of the hood cabinet which will probably be around 16-17" high to seamlessly integrate the pull-out. See inspiration below.