Now we are getting someplace. Some random thoughts that are worth what you paid.
Truss spacing has nothing to do with roof load if you are using an engineered package. Wider spacing equals heavier trusses. Price both and compare. The ceiling you install will dictate the nailer spacing. Sometimes closer is cheaper. You cannot take the same truss and widen the layout without compromising the values.
I have not put in a 9' wide overhead door for 20 years. The difference in cost for at least a 10' is far cheaper that replacing an electric/heated mirror once. With kids driving also I think you understand.
Consider house wrap under the steel panels. Steel will leak a lot of air when its breezy.
A 48" wide walk door is 100 bucks more that a 36". If that will let your mower etc. pass without opening a larger door its probably worth it. If you want a little more room a 6' x 7' overhead is much cheaper than a double walk door.
Length is cheaper than width as you have already bought both ends.
In my shop the car lift works just fine with a 12' ceiling unless you opt for the heavier bus rated ones. Possible a raised lower chord truss is an option.
If you go with the shorter doors consider a vertical lift track so the horizontals are not hanging down below the ceiling. Jackshaft operators work well with this system.
Insurance is considerably less with UL listed steel. (30% or more)
When I install radiant heaters I will try to utilize a raised lower chord truss mentioned above to allow more room for the unit to be installed. No fun to melt stuff parked underneath of it.
Prep for gutter even if you never install it,
For the most efficient building we use SIP panels. If you are going to climate control the interior its the best route.
Be sure to taper the concrete under the overheads or water will run in vs out.
Good luck
