Wildfire Zone

I think non-vented can be done but if the house is too tight you may need some sort of HVAC system to bring in fresh air. There are some firesafe vents made primarily in CA that close down at high temps, to prevent ember intake. I think all metal roofs can be installed to prevent ember entry but mechanically seamed standing seam might be the "tightest" way to do things. Are you planning on steel on the walls as well?

What is the design of the home and what region of the country?

Building to code is going to dictate what levels you need to insulate too, however, a sealed roof design is certainly more preferable for you.

Is the roof going to be SIP, rafter, or truss? Are you in the design phase?

I am in the design phase. Single story. Not sure yet re SIP, rafter or truss- I am flexible ible on this but just a layperson and just starting the process. My home-site is in southern california, away from coast, in region that recently burned with wind blown embers at >70 miles per hour and chapparel for miles adjacent to my home. So my first priority in design is fire safety, in particular preventing embers blown by high winds from entering roof assembly.

Is there significant improvement re minimizing risk of ember entry in small spaces using vertical/ standing seam vs pre-formed panels or granular coated panels?