In this Unreal Engine 5.3 Niagara tutorial, we explore the Spawn Per Frame module and look at how it differs from the standard Spawn Rate. Learn how particles calculate on every single frame to avoid empty gaps in your timeline and how to use conditional spawning effectively! 
https://dev.epicgames.com/community/learning/tutorials/7xmMa/unreal-engine-ue5-3-niagara-basic-spawn-per-frame-13