The trichomes continue to develop even after you harvest.
But it doesn't mean that you can harvest early and let the trichomes mature while you dry & cure since your buds will not be fully developed and you'll end up with airy/small/underdeveloped buds.
I cannot give you a precise answer regarding your early harvest chop without knowing more about strain, conditions etc.
There are so many variables that play into it, no one could possibly answer that question fully or factually.
If it's a slow flowering plant, you might not see much change if it's not you might see 5%-10% change, but then again, temp, RH, drying time, curing time etc. all affect this.
You just need to keep in mind that the trichomes will keep developing and that you should take care in the drying & curing process (especially with temp and light exposure and handling) to not lose any trichome nor cause any THC to degrade more than what is normal (exposing your buds to UV light and high temps can cause this).
What you should take away from the 'trichomes keep developing' statement is that you should never harvest too late, since you won't end up with the amber % you had when you harvested (because trichomes keep degrading (in case of cloudy to amber) / developing).