I passed my ISC2 ISSEP exam last week. It was harder than CISSP for me because it focuses a lot on systems security engineering. This means you need to understand how security fits into building and designing systems, not just security rules. If you don't have an engineering background like me, some parts like NIST SP 800-160 can feel confusing at first.
What helped me a lot was practicing questions from ITExamsTopics. Their ISSEP questions are similar to the real exam, with real situations instead of just definitions. I also spent extra time on the security engineering part because it connects everything together and many people skip it. If you're studying for this exam, feel free to ask me anything.