My parents' house was built in early 70's, has original site-built dark oak cabinets with crown molding going all the way to ceiling. My mom just put in granite and tin backsplash a couple of years ago. Their ceilings are less than 8ft (7' 6" or 7' 9" I think?). I don't think there's a minimum ceiling height required for crown, though I think a maximum gap of 6" b/t the top of cabinets and the ceiling looks best if you're trying to bring the crown all the way to the ceiling. Any more, and you'd have a huge filler between the cabinet and the crown. With 8ft ceilings and "standard" 18" backsplash, you'd need 42" cabinets to go all the way to the ceiling. Crown would be less expensive. Something to think about. I agree that crown "finishes" the cabinets nicer than a factory (particleboard) edge, but if your cabinets go all the way to the ceiling then you don't need crown (though you might need a thin piece of some kind of trim to hide any gaps since your ceiling probably isn't flat). Do what you want, not what you think the trend is (I'm assuming you're not remodeling to sell).

The size of uppers that you can use depends on how much crown molding that you want, as well as you understanding that tall doors have the tendency to warp over time. Which is why tall ceilings tend to have stacked cabinets over having taller single doors. You can do: 42" tall cabinets, with standard or stacked crown, leaving space on top. Standard 42" cabinets with 12" of molding, which can be top heavy. The corner cabinet shown below is 42", with about 6" of molding, and the lower wall cabinets are 36" with the same 6" of molding. [[(https://www.houzz.com/photos/kemper-echo-wine-bar-traditional-wine-cellar-phvw-vp~8377733) [Traditional Wine Cellar[(https://www.houzz.com/photos/traditional-wine-cellar-ideas-phbr1-bp~t_755~s_2107) by Other Metro Kitchen & Bath Designers ProSource Memphis 54" tall single door uppers, with no molding, which can really highlight the unlevelness of the ceiling. 51" H cabinets with 3" of crown, which has the same out of level ceiling issue. 48" single door cabinets with 6" of stacked crown molding that disguises the out of level of the ceiling. Same with 45" H cabinets and 9" of a stacked crown molding. Lots of molding can be just as expensive as the taller cabinets. And tall single door cabinets can warp much more than their shorter cousins over time. The corner cabinets shown below are the 48"H with the stacked molding to the "ceiling". [[(https://www.houzz.com/photos/dynasty-omega-showroom-vignette-transitional-kitchen-phvw-vp~8549929) [Transitional Kitchen[(https://www.houzz.com/photos/transitional-kitchen-ideas-phbr1-bp~t_709~s_2112) by Other Metro Kitchen & Bath Designers ProSource Memphis 30" cabinets with 18" cabinets stacked on top, and 6" of crown molding, which can be a more expensive approach because of the stacking. (Same with 33" cabinets with 15" stacked on top, which would be more proportionate to the 2/3-1/3 pleasing proportions.) The pantries below show the 84" H cabinets (same top alignment height as 30"H cabinets) with separate 18" H cabinets stacked on top. The seam between the two on the side is concealed with scribe molding. [[(https://www.houzz.com/photos/mudroom-organization-by-kemper-echo-transitional-laundry-room-phvw-vp~11312364) [Transitional Laundry Room[(https://www.houzz.com/photos/transitional-laundry-room-ideas-phbr1-bp~t_753~s_2112) by Other Metro Kitchen & Bath Designers ProSource Memphis "Prestacked" cabinets. that are 45" H (which in my medium priced line that I use, simulate 30" with 18" on top) This is my Kemper display with the "prestacked" uppers. Note that the oven cabinet had to have a refrigerator cabinet stacked on top in order to line up. [[(https://www.houzz.com/photos/kemper-showroom-vignette-contemporary-kitchen-phvw-vp~8376626) [Contemporary Kitchen[(https://www.houzz.com/photos/contemporary-kitchen-ideas-phbr1-bp~t_709~s_2103) by Other Metro Kitchen & Bath Designers ProSource Memphis

When the cabinets are mounted with the top above the window height, you needn't worry about the projection of the crown interfering with the window molding. If they are lower, then yes, you need to account for the projection of the crown in the design. Crowding window molding is not a great look, either way. I try to go no closer than 3" to a molding, and some kitchens demand more negative space than that. What you run into with very tall cabinets is that it renders the kitchen off visually. I prefer transom cabinets that can break up that long vertical line visually. This is what 9' ceilings with 48"H transom cabinets (30+18 combo) looks like with a 6" cove molding. The cove really needs a riser to account for an out of level ceiling and to make up the tiny bit of difference between the molding height and overall height.

Eight-foot ceilings in a home that does not already have architectural features are better left alone, without trim. I would choose a softer ivory white for the trim and use that color for the ceiling also.