When doing an attached ICF garage, the most economical way would be to share the ICF wall with the house/garage. What is a good ICF wall height at the main car entry point?

There's more involved than 'economical', or there should be. Garages are ugly (even though I love them), and integrating them into the house design should be given some thought. I moved our garage back about 2', and lowered the roof line to minimize the appearance. If I ever get around to it, I'd like to build some nice carriage doors to further improve the looks.

Our garage is not ICF because we are in a mild climate, so didn't need the added expense. The wall with the overhead door is 9'. Most garage doors need more than 8' for enough clearance. They do make low clearance door tracks, but I'm not sure how low you could go. If you have a tall vehicle, you might need a taller door. My 3/4 ton van won't fit under our 'standard' 7' high door, but the one-car garage was built for my wife's car.

Yep, you typically need 11"-12" above door height for a roll-up garage door track/rail system(and opener). So if you plan on using a roll-up door, the wall height may be determined by how tall the door opening needs to be if you need to accomidate a taler vehicle.

I did 11' walls with a 9' door, so had almost 2' of ICF over the door.

If you do a house with larger overhangs and a steep pitch you will not end up with much area over the opening before you hit the soffits.

I did 16 inch energy heals, 16 inch overhang, 8 inch fascia boards, with a 10/12 pitch and still lost 4 inches of visual wall over the openings. Without the energy heals the fascia boards would have been covering the opening to the garage; it would have looked funny and reduced how tall of truck I could fit in.

Side note, I did scissor trusses also. The high lift garage doors needed to angle up the cathedral walls instead of straight into the garage cost $250 extra per door. I didn't think it cost that much more for the extra seven foot of head room I gained for my hoist.

Most of the attached garages we do have a step down from the house. That helps with the height issue. I'm also old school and we live in the frozen tundra, so I try to encourage the garage door to be on a gable end of the garage. That eliminates the need for a larger header or lintel.