Do Cut it back for winter. This is one with the "big dinner plate size blooms" I've munched and soiled the roots.
You should only cut the dead blooms once they are done. In the spring you may prune out any dead growth, but I wouldn't cut them all the way back, as this will hinder the flowering process. Here is an article for more information: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm