Needinfo1 - what Tom meant by recessed is a canopy hood. I.e. don't buy one of those flat hoods, even though they look cool. Also, the curved glass ones aren't so great. A canopy hood will capture best the rising smoke and grease. To the OP, a 30" hood will be fine. The hoods that are 36" wide over a 30" hood are the ideal, but so many of us cannot afford to forego the upper cabinetry for the 36" width. You should get a hood that is not a skimpy depth of 20-22". Those won't cover the front burners. As Tom said, a 24" depth hood would be good. Your question about 600 cfm vs. less cfm: it is better to have the 600 cfm, even if you don't use it that often, say, for searing steak, than to have an underpowered hood, and have to have it on its highest setting all the time. You'll have less noise if you can run your 600 cfm hood at medium or low, and still have the hood be effective, than if you are running your 400 cfm hood on high all the time because it is underpowered. Make sure your exhaust duct is sized properly. Most hoods specify an 8" or 10" diameter duct. There are some hoods that allow a 6" diameter duct, but they're harder to find. The problem with pushing too much air through too small of a duct is that you will get increased noise and decreased efficiency though no fault of the hood. So check your exhaust duct size (if already installed), and match your hood to it, or if still in the construction stage, install the right-sized duct.

That was a common layout several decades ago. I would be inclined to do do a major re-arrangement, but I would be doing most of the work myself and I would have to consider budget, as well. We work with the budgets and spaces we have. I'll offer some considerations about the existing space and the questions you asked. Is 17.5" too close for an OTR over a gas range? No. People put all kinds of gas ranges beneath OTRs including "pro-style" ranges. There's a photo of one over an NXR in the discussion that I've linked below. Note that the base of this one was only about 4" higher than yours -- maybe 22" above the range. While your OTR could be easily (well, relatively easily) vented to the outside, swapping in a higher powered gas range presents a couple of things to think about. One concern is "coverage." It isn't very good with an OTR. Basically, an OTR is mostly venting just the two back burners. This is not a fire hazard concern but, rather, an annoyance, It means more heat and more goo in the kitchen than with a dedicated vent hood. The other concern with OTRs over gas ranges is a suspicion that waste heat from a gas stove may contribute to eventual failure of the microwave part of the unit. Frankly, though, microwaves are such a commodity product these days and often so cheaply made that it can be hard to determine how much havinga gas range contributed to or accelerated a failure. Also, consider how often you will be using all the gas burners on the range on full power at the same time. Also, you don't avoid waste-heat problems by going with a radiant electric stove. They just make somewhat less waste heat, but not hugely so. IIRC, radiant smoothtops put 50% to 55% of their energy into pans, so roughly half of the energy can go into the room as waste heat. . With gas ranges, the rating is 33% to 40% going to pans. That's about a 20% difference, which is not huge. Coil burners are closer to 70% to 75% of energy going into pans and induction is rated at 85% to 90%. The latter differences are significant and may affect your planning about what to do with your kitchen and range replacement choices. The 30" height-above-the-stove recommendation for hoods is mainly to get them out of the way so cooks don't bang their heads when leaning over to stir or look into a pot. Another consideration that may affect your planning is that In your current kitchen layout, a hood is going to project out at least another 10 to 14 inches fruther from the cabinets. In the present location, that that could crowd (or seem to crowd) into the space expectations of folks using the sink. You can get a relatively shallow venting appliance --- can we really call them hoods if they don't have a canopy? --- which may mitigate the distance from stovetop to hood/vent somewhat. Not ideal, but workable. For example, my old house kitchen layout is such that I went with a 5" tall Zephyr hood. There is another 30" minimum clearance requirement that sometimes gets confused or mixed in to these discussions. That is for when you don't have a hood, and then the unobstructed distance above the range to flammable upper cabinet bases is generally specified as being at least 30 inches. An OTR or range hood are regarded as non-flammable surfaces so they can be closer. If you swap in a hood, what to do about a microwave? Apparently, you use the convection features a fair amount? (Otherwise, I'd suggest a cabinet hung MW unit elsewhere in the kitchen.) Do you have room for a cart someplace to hold that GE convection mw? Is there any kind of a pantry space where you could put it? If not, then maybe you just vent the existing one to the outdoors. Then give your self some time to plan and budget for a more extensive revamp. Here is a link that might be useful: Thread with photo of Nunyabiz's OTR

I don't think you will notice after a while. Mine is off by about 1" on the left, because the *&^&%$ range hood is a full inch less wide than the rangetop (I swear I bought a 48" range hood, not 47"!). But then again, we are DIY so I wasn't about to make my poor DH uninstall then reinstall all of the lower cabinets after it took him a full day in the first place; if we were paying someone for it, it might be a different story. If you choose to keep it, just make sure you don't do a stacked tile BS - you would probably definitely notice it then. Example of what not to do: http://www.peeltile.com/img/media/backsplash/layout.jpg

Ideally the hood should be 6" wider than the range. I think the recommendation above to go 12" wider than a 30" range is overkill. "reasoning was something along the lines that with a bigger hood, you can install it a little taller (looks better) than the recommended distance between stove top and base of hood." Either you misinterpreted what you read, or the person who said that is misinformed. I think what you are referring to is that a taller canopy-style hood will gather and contain, i.e., capture, the smoke and grease better than a more sleek-looking flat glass hood for example, or the smaller undercabinet hoods that are 3-6" tall. In addition, a taller hood has more of a wow factor and presence in a kitchen. I would not equate a taller hood to being able to install the hood a greater distance above the range. Also if you install a hood too high above the range, the proportion can begin to look odd. Most of all, installing the hood too high above the range gives the smoke and grease more opportunity to escape. You wouldn't want to spend all that money on a hood and then curtail its efficiency by installing it too high. The ideal height is a 30-36" distance between the top of the cooktop and the bottom of the hood. I didn't see any mention in the OP of exhaust duct size. Duct size is important. You could buy the best hood in the universe, but if the duct is not sized appropriately, the hood will have decreased efficiency and increased noise through no fault of its own. The most common required duct diameters are 8" and 10". The hood's specs will say which. For a 30" range, the 36" hood will most likely require an 8" diameter duct. Hoods that require a 10" duct typically are for 48" ranges or larger. Do NOT give in to your builder if he says "I am sure a 6" duct will be fine". That might be an easier installation for him, but you have to live with it.