If you have moulding on the window, you can probably hide the difference there. We have a 3/4" difference in moulding on either side of a window because of a wall and I worried endlessly at the time, but no one (including me!) notices it. Ditto for our sink cabinet and sink being slightly off-center (also for structural reasons that we weren't willing to pay to change--100-year-old studs in the way!) Worried a lot, but haven't thought about it since we finished--your eye assumes symmetry if it is close. If you can get it down to half an inch or less by playing with the moulding, it likely won't be noticeable. If you can't, maybe you can rehang the cabinet and go back to having some filler on the other side?

It depends a lot on how you use the kitchen. DW is 5'4" and I am 5'8" so we're very similar in size. I went with 19" because I use a tilt up mixer a lot and when I've had a lower clearance I've felt it really affected my sight lines/made it harder to see what I was doing. On the positive side - It does make the higher shelves on your uppers easier to reach. Are you planning on any undercab lighting? If so what kind and how will that affect your clearance? I know a lot of people are opposed to this, but I actually like a slightly shorter counter height so I had 3/4" shaved off of my base cabs (but not the island where the range is) . I asked my GC who was extremely knowledgeable if I could shave off an inch and the max he advised was 3/4". He was right - more would have been trouble. I'm happy with it so far and don't think it's that noticeable. It could bother someone at resale time, but I'm willing to live with that trade off for a counter height that's more comfortable for DW and myself. If you do shorten, you want to be very, very careful about measuring your DW and range. My brand new Bosch DW had problems and had to be swapped out with a new one. The repair person who swapped them out (not the original installer) was not pleased about the clearance but did manage to get the new one in. Also, IMO, This is the kind of thing a KD should help make the right decision on, not make a bad decision for you without consulting you. They absolutely should have checked with you about this. If this can't be fixed easily, I would ask them to make it up to you in some other way.

I learned something interesting from my contractor when we discussed mounting the wall cabinets a little higher so I could have enough space for certain appliances as well as a light rail. My contractor told me that I'd need to customize the cabinets by either reducing the height of the wall cabinets or increasing the height of the full-height cabinets (like the pantry and double oven cabinets.) Otherwise, mounting wall cabinets higher would result in cabinets where the tops don't line up. jayne p.s. I reduced the height of the wall cabinets to 34 1/2. I probably could have been fine with 35 inches but there's no way I would have known it until the end of the installation so better this way than not being able to cover the undercabinet lighting.

I think the 20 or the 21 will be fine. (a lot depends on all the other elements in the room, so you'll need to consider that too) this one looks like a standard 18" This one looks to be a little taller. This one too. The height of the cabs come into play. a 30" or 36" cab raised to far off the floor w/a ceiling like this, can look squatty. I think a lower this a tad and doing a taller crown would have looked better. IMO I have a lower ceiling. my cabs are 36" and 18" from the counter I have a mixer that barely fits under the cab. an extra inch would have been nice. This one recommends 18" https://www.bobvila.com/articles/upper-cabinet-height/ The ideal upper cabinet height is 54 inches above the floor. That is, the bottom edge of the upper cabinets should sit 54 inches off the ground. This magic number combines the 34-½-inch height of a standard base cabinet (those that sit on the ground), a standard countertop above it with a thickness of 1-½ inches, and a standard 18-inch backsplash (or, in lieu of a backsplash, empty wall space) between the top of the base cabinet countertop and the bottom of the upper cabinet. If your base cabinet height, countertop thickness, or backsplash/wall clearance height will differ from the standard heights above, you’ll need to adjust the upper cabinet mounting height so that it represents the sum of these three heights. Measuring the upper cabinet height from the ground is recommended when the base cabinet and its countertop haven’t been installed yet because you intend to install them after the upper cabinets or because you never plan to install base cabinets in the room (e.g. in a laundry room that doesn’t need them.)