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will I notice
Who knows, your sensitivity is a mystery to us. You can do all the maths for yourself, but in addition to increasing stack by about 14mm and very slightly reducing reach, you will also be reducing BB drop by about 6mm, reducing the head and seat tube angles by nearly 1° and, assuming no change in fork offset, increasing trail by about 6mm. These are all changes which lie within the normal range of variability, but they vary between bicycle use cases for reasons, and not usually in the same direction as using the wrong fork changes them, e.g. if you slacken the angles and increase trail to turn your road bike into a touring bike, you would usually increase BB drop, not reduce it.
I'm sure you will be able to ride around the "problem", and even come to see it as normal, but you may always have a nagging suspicion that your bike isn't as nice as it used to be.
Maybe a bit vague/silly question but will I notice the difference going from a 385mm axel to crown to a 400mm?
I get it's going to lift the front a bit, but is it just going to be like switching between a 80 and 110 stem, where you notice it initially but soon forget?
Cheers.