I read it as 2400 or 2700 windows and doors, the ceiling was a typo.and should have read window. The ceilings are all 3m The 2.4 could work are you able to post any plans 2D & 3d to give us a better perspective, there's so much to consider with anew home

2100 is standard for internal and external doors. The cupboards don't need to match the standard. The cavity doors may be taller for some other reason (to accomodate the track?).

1800mm on a 2740 ceiling height is small. What height, off the floor level, are you starting your 1800mm windows? If you started them at 500mm from floor level, this would give you are nice high window. It would be the cost of the extra wall from floor level. weigh this cost against a 2057mm window. I have 2740mm ceilings and all my living windows are stacker doors at 2340mm. If you are having curtains, you could have your 1800 windows, and have the curtain drop from the cornice of the 2740 ceiling height. This would disguise the low window. But then this also would be an extra cost for the length of the curtain.

If you are referring to the plan posted on another discussion, you only have three windows on the facade, so it would not be a big design choice. I personally prefer 2430mm doors and windows with 2700mm ceilings, and standard height window and doors for upstairs 2500mm ceilings. But every increase to window and door height costs more money, so it goes back to budget.