Kabalah

I’d like to find someone to ask the following.I understand how in Toras Niglah you can have someone like the Ketzos or R Chaim say a chiddush that other people see is correct and are mekbel, but when we say the Arizal said new things in Kabalah and that the dor was mekabel them, in what sense are there new things in Kabalah, and how can a dor that didn’t have a mesora for them verify that they are correct? Perhaps both are a type of ruach hakodesh, but I haven’t seen it said anywhere.