Original cooktop

More powerful

Original hood ordered.

Generally, for residential cooking into real hoods, the momentum of the cooking effluent determines the need for sufficient air velocity into the hood. This is not a function of cooktop BTUh except partially, but of both burner output AND pan temperature AND oil or grease type being vaporized.

Here is a short summary in the form of directions:

• Select a proper baffle filter type hood 42 inches wide and at least 24 inches front to back.
• Calculate hood entry area: 42 x 24 / 144 = 7 sq. ft.
• Set achieved CFM to 7 x 90 = 630 CFM
• Choose a blower than is rated at zero static pressure to be 630 x 1.5 = between 900 and 1000 CFM.
• This should be sufficient for hood bases set up to 36 inches above the pans.

Many other details need to emerge such as duct path, external or internal blower, silencer if you want quiet, etc.

Other things:

• One hour is far too little.
• You will most likely need make-up air (MUA) and the form it needs to take for your application will also need to be studied
• You do not need the hood to be the same brand as the cooktop
• It is better if the baffles sit in the hood at an angle and there be some volume below the baffles above the plane of the hood base
• For residential hoods, I think shapes such as on Wolf's Design Guide pages 153-154 (2021 guide) can provide the baffle space needed and assure smooth flow into the duct. You can buy other brands.
• Gas cooktop installation instructions need to be carefully scrutinized, particularly with respect to distances to combustibles. This includes combustible inside the back wall. A backguard (riser) may be needed if your cooktop is too close to the wall. Island trim is for islands.

Kaseki, thanks for your reply.  I appreciate the time and energy put into your response.  That said, much of what you have said is beyond my understanding.  I was able to glean a few things... Sounds like we need a 42" x 24" hood with a CFM between 900 and 1000.

Another thing you mentioned
"Gas cooktop installation instructions need to be carefully scrutinized, particularly with respect to distances to combustibles. This includes combustible inside the back wall. A backguard (riser) may be needed if your cooktop is too close to the wall. Island trim is for islands. "

I brought this up with my husband, our contractor and the appliance store main guy.  They all dismissed my concerns saying the metal beams were unnecessary and having white subway tile on the backsplash were fine.

Kaseki... Sorry bumped the send!
As I was saying, no one in my small town seemed concerned.  I showed them the Cafe installation diagrams.  It says something about 12" clearance from combustible materials.  Tile over drywall over wood studs didn't seem ok per the instructions.  All 3 men thought I was over the top.  Am I wrong?

Where are you in your build? Have you ordered your cabinets? Is your budget stretched thin already? All these things will come into play. As Kaseki mentioned, you will need make-up air (by code generally) and that is not cheap. Are you working with a kitchen designer?

What kind of cooking do you do? Might you be okay with a less powerful range? And then there's your countertop dilemma. There are so many questions, and professional guidance could really help you make the best decisions for you and your family.

On the other subject, the countertop, a seam might be almost invisible depending on the pattern of the material. See if you can find examples. It might be fine!

Any kind of vein (marble) pattern will show a seam in quartz, unless you buy book matched. Only a few companies offer book matched slabs. All over patterns are easier to disguise but in general, natural stone (bookmatched) is better to seam than quartz, unless its a plain quartz and even then you have to make sure the slab colors are the same, of the same lot.

Several threads here, often started due to heat damage to resin-based backsplashes (e.g. Quartz), have topically deviated into the requirements of the International Mechanical Code (Table 308.4.2). However, one doesn't need to interpret that code oneself all the way to the cooktop installation details. The manufacturer and UL, CE, CSA, etc. will determine the minimum safe distance and put it into the installation instructions. Your local code enforcement officer should be checking actual installations vs. manufacturer's installation directions for compliance.

I can't read the installation scans you have provided, so I can't determine in which direction they might have limited combustibles w.r.t. a 12-inch distance. Generally, having combustible materials in walls, particularly the studs, close to heat sources can subject the wood to heat damage that slowly degrades strength and fire resistance due to distillation of chemicals in the wood. As a result, more powerful gas stoves have accessory/optional riser/back-guards that provide a heat buffer. If you looked at the designs, you would probably note similarity with some examples in the IMC table I referenced above.

I can't do your safety analysis from here. One of my town inspectors once asserted somewhat in jest that the reason for code compliance was to limit the income of insurance company lawyers (who would be using lack of code compliance to get out of paying for damages). I think building code compliance is one of those situations where the maxim "it is better to ask for forgiveness than permission" is not applicable. Check with your Authority Having Jurisdiction (AHJ) for an opinion. Perhaps modifying the wall won't be a big deal on the scale of the entire kitchen part of the build.