Trying to find a way to load Niagara Systems before the first use so it won’t wait.
I would say ‘load asset’ node 
You’ve got sync and async
I would say, though, that if you already have a hard ref to the particle system, then it is already loaded…?
There isn’t, it’s a Spawned effect.
Just having the type in the spawn node, is a hard reference.
Otherwise, you can use this asset load system