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(below is my interpretation of what I've heard from people who know JVM better than me, take with a pinch of salt)
Okay, so, JVM flags. You know them, and you either love or hate them.
Honestly? The default flags are the best for general purpose use. After all, they're tuned by the OpenJDK people, and they know best about OpenJDK.
While someone sufficiently knowledgeble about JVM internals and the specific hardware-workload combo can apparently tune it to be better, there's no silver bullet flag set.
After all, if there was a silver bullet flag set that improved performance every time, OpenJDK would adopt them as default, they're smart people after all.
While you can get improvements by selecting the best GC for "general MC workload", that is one or two flags at most(and is presented by this semi-parody website) and requires at most two braincells to understand.