The reflection of each "ray" of a cooking plume off of hood surfaces should be in the direction of the baffles. A flat undersurface if fully baffled is not desirable, a flat undersurface only partially filled with baffles is even more undesirable. Hence, from this point of view the Kobe is less deficient than the IKTCH, unless the IKTCH were itself sunk into a metal surround that provided some volume under the baffles.

Neither looks like it has the front-to-back distance to overlap the cookting zone in that direction.

Do these, with pressure losses, achieve 90 CFM /sq. ft. of bottom surface area?

I have a 36 in range. And I read I can go 36 or 42 for the range hood. I am unsure of the 90 CFM/sq ft. The iktch is 900cfm and the Kobe is 750cfm. My kitchen is 375 sq ft.

42 is better for capturing expanding cooking plumes. And the rated CFM is not the CFM you get; it is the free air CFM with no baffle or other factor pressure loss.

Assume a 42 x 24 hood aperture (7 sq. ft.). Then the desired flow rate is 90 x 7 = 630 CFM actual (for hot oil cooking with residential style hoods). Allocate a factor of 1.5X for pressure losses assuming some reasonable stab at a make-up air system. This gets you to a 900 -- 1000 CFM rated blower.

Note that a lot of approximations are involved here, and some restriction on which burner is used for heavier plumes, or use of induction to remove the gas combustion part of the plume, or only boiling eggs may allow somewhat more modest flow rates to be sufficient.

Note that this flow rate will require make-up air to achieve, and to protect against back-drafting of combustion appliances, if any.

Please review the many hood and MUA threads here for perspective.