You are not crazy, and ducting is among the most vague things about kitchen work. Complicated even more by the fact that most appliance guys are kind of clueless.
Venting boils down to a few things. Size of the duct, length of the run, turns/obstructions in the run and blower/hood configuration.
First you need to think about what you cook. If you boil water and do light family meals, then 450CFM out of a basic hood will likely be ok. If you do high heat or high grease cooking regularly you need something more substantial both in size and in CFM.
Second look at how much space you have. Round Ducts are most efficient and most basic hoods call for a 6" round duct as a minimum or the equivalent. If you have to do rectangular that's ok too...just make sure it meets or exceeds what the manufacturer is asking for. If you have the space to go straight up with few turns you should be able to get a pretty effective setup. If you have to turn a few times, you need to add more power (think of it like an engine in a car, the heavier the car the more horsepower you need i.e. the more turns and restrictions you need, the more power you need to overcome them)
Then if all those things match up, the hood style itself will play a factor. A pro style, boxy hood will provide more capture space than a flat bottomed chimney hood. Mesh filters are better for grease filtering, but need to be cleaned more often because they can clog or become a fire hazard. Baffles are better, and need less cleaning, but will make the hood noisier at low speed.
If you want to, let us know what type of range and cooking you are putting in, and we can help you select an appropriate hood, or at least help narrow down your choices.
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Mix of wood with white cabinets, backsplash, and black trim on windows.
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