Unreal Engine provides several different tools you can use to help debug what's going on in your simulations.
Optimizing your Niagara System
Niagara Debugger
If you need to further debug Niagara simulations after they've been added to your level, then you can use the Niagara Debugger. This lets you turn on a heads-up display (HUD) that outputs detailed information about the simulations in your level, such as the number of particles being generated, the amount of memory being used, and more. You can also capture a snapshot of information and then analyze that output.
Performance Budgeting Using Effect Types
Create a new type of asset called a Niagara Effect Type to configure a variety of settings to help you manage budgeting in your level. Any Niagara Systems that use this Effect Type will inherit the rules you set. This way, you can improve performance by, for example, culling systems that are a certain distance away.
How to Fix a GPU Crash
As some Niagara simulations can be graphically intensive, working in those scenes in Windows could cause a GPU crash. Visit this page to find out more about how to resolve it.