I would not go smaller than 10" on your ductwork. The larger the duct the more air it will flow and the quieter it will be. 1000cfm sounds like overkill for an induction, but if you are getting a grill on a CC then it would be required. The overall duct run is not very far, as long as there are not alot of elbows. Elbows restrict airflow and increase noise. Remote blowers will decrease noise if they are far enough from the hood (usually over 5').

My mom had heat lamps on her VAH. There was a separate shelf option with fold-down wire shelves. She said it was the thing she liked most about it.

So what is the right size blower for an induction? 400 cfm? 600 cfm?

This may be heresy, and it's a bit backwards, but if you are undecided about what cooktop you want to get, then just don't do a hood at all at first. Go ahead and put in the 10" ducting, because you can always slip an 8" duct inside if the hood you end up using works better with that. But as long as you have easy attic access, you can put the blower any darn where you please when you decide how strong of a hood you want to put in.

A gas range has a lot more excess heat produced than induction so the two ventilation needs are different. I think most people could get by with a 600CFM on induction as long as they don't plan to do a lot of high heat searing and stir frying. If you do, then go up to 900CFM. For a gas range, 600 CFM is where I'd start with a 30" cooktop with decent BTU power. More BTU's and larger mean more CFMs and larger hood.

So you really need to finalize your cooking equipment before finalizing your venting equipment.

First, hood size should be selected to assure capture of the rising effluent, which expands as it rises at about 22 degrees half angle from the entire hot pan surface. While an induction surface is relatively cold, the effluent you are trying to collect comes primarily from the hot pan. So a gas surface just adds additional rising heat because some of the heat generated misses the pan.

Second, choose a cfm that for the hood design selected assures containment. This is vastly easier said than done, but essentially you want the velocity of the air entering the baffles times the area of the baffle portion to be at least that of the rising effluent, about 3 feet per second. Even better would be 3 ft/s at the hood aperture, particularly if the aperture is a flat surface with a mesh filter.

Or, you can guess and say that for serious cooking you will probably want at least 600 actual cfm. Note that this is the cfm achieved when all pressure losses are accounted for on the fan curve (cfm vs. pressure loss). Given baffles, duct transitions, negative house pressure without good make-up air, etc., you may need a 900 cfm rated fan to actually get 600 cfm.

Next, size the duct so that the 600 cfm that is being extracted from the house has enough velocity to minimize particle and vapor deposition on the duct walls. This is at least 500 feet per minute for warm ducts, and at least 1000 fpm if the duct passes through a cold attic during part of the year.

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