900 cfm is adequate, you need 30 inches and THEN the wood hood, and NOBODY can advise minus the specs for the hood insert you select, or without knowing range, style of hood or anything else about your kitchen. You have TWO posts, stick to one.

Best advice is get a kitchen designer on your site.

Some of your questions have been answered many times on this forum, and review of many hood threads will reveal the rationale for the suggestions. Here is a very terse summary:

For a 30 inch range use a 36-inch wide hood to overlap rising and expanding cooking plumes. Try for a 24-inch front to back distance, and mount the hood high enough to not hit one's head when bending over the range. (Up to 36 inches with this size)

These dimensions give an entry aperture of 3 x 2 = 6 sq. ft. Aim for 90 CFM/sq. ft., resulting in a requirement for 90 x 6 = 540 CFM. This has to be provided in the context of the blower's fan curve, the baffle, hood, and duct pressure losses, and any make-up air pressure loss. As a rough approximation, multiply 540 x 1.5 to obtain 810 CFM, the minimum zero static pressure rating of the hood system blower. Plan on having to have a make-up air system; see relevant threads.

Hoods by their nature have to be steel, but can be made without elegant steel exteriors (hood insert) and covered with wood cabinetry. So long as hood cabinetry and nearby cabinets meet the required distance from the range to combustible materials, there is no reason why the cabinets cannot be connected to the hood cabinet-like exterior. You will see many examples just by looking for them. Most major hood manufacturers sell stand-alone stainless steel hoods and steel inserts for wooden cabinet enclosures.

Suggestions:

Download from the SubZero/Wolf web site the Wold Design Guide and study the hood portion to see the types of options that are generally available for hood styles and configurations. Broan/Best/NuTone, Modernaire, Abbaka, and others have web sites with information.

Download the Greenheck Guide from the link below and review the first dozen pages or so to understand what it is that the hood is intended to accomplish.

https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf

There is a hood FAQ here under forum member @opaone's name, as well as a perspective article at https://bamasotan.us/range-exhaust-hood-faq/.

"you need 30 inches and THEN the wood hood"

Just to correct this. As @kaseki said, you should have a 36" insert and THEN the wood surround.

Thank you sooooo much!! very very helpful! i was getting lost if i need 36 inch hood and 36 inch insert and i couldn’t understand how the insert will fit in the wooden hood if they are both 36 inch. i am checking the links to find out more about it and the safety sonce it is wooden hood. Thank you all so much!

The skin has little to do with the organs contained...............: ) within it. The insert is an "organ"

Historically, the off-the-shelf hood inserts have been undersized relative to the standard hood widths so that the cabinetry has common dimensions. The image below is from the 2021 Wolf Design Guide for "Pro" hoods. These dimensions force the user to go a bit undersized with the hood aperture; however, flow at the hood or insert edges may make the effective width close to 36 inches (for this thread's example).

Standard hoods in standard sizes also have wall thickness, so they too have undersized apertures, but unless one wants to examine a cooking plume for velocity vs. angle versus the hood for velocity vs. position at the boundary edge, we just ignore the issue because all of this subject is approximation unless computational fluid dynamics is used to analyze a specific case.

For reference, my Wolf Pro Island hood's exterior width is nominally 66 inches, but the interior aperture width is only 61 inches. This is due not only to wall thickness, about an inch at each side, but to exterior shape.