Cresties usually are not difficult to get to cool, females will naturally respond to even slight drops in the ambient temperatures and changes in light (shorter days) and stop laying. Those who adopt artificial cycles for whatever reasons may need to adjust their inside lighting and temps accordingly, however. It can be difficult (and expensive for the electric bill!) to induce females to cool during the summer if they have laid through a winter, however, which is why I personally prefer to follow the natural seasons.
Cresties do not typically brumate, though they often eat slightly less and do not grow as quickly (if at all) during the cooler months. Their activity and growth rate depends on the temperature they are kept, for the most part. This part applies for Cresties of every size and gender.
Yes, females do need a 4-6 month "cooling" period where they are not laying and their bodies are given time to recouperate from the stresses of breeding and laying. Some females may need to be given a year off, depending on their condition (some breeders I know only breed females every other season or give their female every 3rd season off)- that really depends on each female in question, as some will lose more weight and struggle with proper egg calcification than others. Some breeders are able to leave their pairs and trios together year round and the females will still enter a cooling period naturally. Others have found they need to remove the male.
Sometimes you may need to take steps to induce cooling in females if it seems like their health is being compromised and yet they still continue to lay... So there really are quite a few different types of scenarios that can come up and IMO really the bottom line is knowing and monitoring your animals combined with good husbandry.