No added window. There will be plenty of natural light wtihout, and it makes the house look more like a house without it. I also feel the house feels less "heavy" on that side without the extra window.

Definitely skip the upper windows. They aren't particularly good looking, and will bring in glare and unwanted sunshine, especially in the morning. Your friend is correct, you will be hard pressed to dress them, and even after spending a lot of $$$ to do so, as Jan says, you'll keep them covered all the time. Waste of money.

Skip the window as long as the other two function as the egress. What is the reason for the truncated gable vs a pure shed roof that would read more modern? Not a fan.

The other window are sufficient for egress. Yes, the truncated gable is a modern design element. The architect has used this element in prior homes - see photo. I'm on the fence on the aesthetic and functionality.

Sorry, but I think it looks like a bad DIY remuddle of an exiting home. A pure shed would be cleaner, which is second cousin to minimalist, which I the first principle of modernism.

I'd be excited to hear from a few more pros.