Your architect is correct about the proportions. Especially if this is one of those wide and deep and already roof top heavy plans like so many of the mills turn out these days. 8' is more than tall enough for rooms where you spend the majority of time in them with your eyes closed asleep. Put the height and space into the public rooms where you live the majority of your life. That's not the bedrooms. Or bathrooms.

The proof will be in the elevation drawing. Until one is drawn the architect cannot know that it will appear "top heavy" especially if there will be a 3rd floor above it. The architect should be able to design a well proportioned house with all ceiling heights at 9 ft.

We have a mix of 9 and 8 ft ceilings upstairs (we didn't build the house) and I much prefer the rooms with 9 ft.

Our previous home had 9' ceilings up and down...and looked perfectly fine. It was a colonial style 2 story. I think window sizes could be adjusted if "top-heavy" is a concern...but I can't imagine that it would be. Every home in our previous neighborhood (production builder) had 9' ceilings up and down...none of the many house facades looked at all strange.

The older row houses that have 14, 12, 10, 8 foot ceilings or 12, 10, 9, 8 foot ceilings on ascending floors look more graceful than the new construction 9,9,9,9 or 10,9,9,9 houses in the same neighborhood. It's a subtle difference, and maybe most people don't notice it, but I think it makes a difference.

We have 9' in the basement, 10' on the main floor, and 8' on the 2nd floor, which is all bedrooms and bathrooms.