Generally 24" is considered the "normal" height above a heated surface. BUT you are in CA, so it would be best to check your local building code office, since regulations there are much, much different than the rest of the country.

 

What does the installation manual for your range say? My GE Cafe range specified a minimum of 30 inches clearance to a range hood. From a practical matter and as guy whose cooking skills are my strongest DIY talents, I suffered with a conventional stove and OTR with 24 inches clearance for years. Contorting my self to see the bottom of any tall pot on the back burners is something I don't miss. The 30 inch clearance is a pleasure to work with and perhaps if I had the room maybe more with a more powerful hood.

 

The appliance manual says 36 inches if hood has combustible material but can go down to 25 if metal. I think i have my answer...Yes i also hate to hit my head on the corner of hoods that are too low

 

Any thing over 300 cfm best to have a window near for fresh air. Hopefully it draws across the cooking surface.

I would check the mounting heights of the equipment your considering. They know what works and what does not. Also can make a difference between gas and electric.