Not enough data. You need to tell how are you trying to create them, from which menu, and preferably provide some code. It is really unclear what you’re trying to do at the moment.
Why would you want to do that?
Particle system is created in editor through context menu->create particle system. You double click it and edit it in particle system editor. The resulting particle system is then referenced from UParticleSystemComponent. As UParticleSystem*, without TSubClassOf. I don’t think there’s any reason to try to derive from it?
IIRC It stores “reference” or pointer to object’s UClass. The one that is returned from ::StaticClass() method. You usually pass that into SpawnActor, NewObject, etc.
Also, you can extract object from that. Call GetDefaultObject(). You probably don’t want to do that with actors, components, and such. Those must be spawned or created.