I have a simple question:
Does it significantly affect the performance to have multiple particle systems instead of just one if the multiple particle systems would emit the same amount of particles as a singular one?
It depends 
Multiple systems will multi-thread better. If your target platforms are multi core.
Multiple systems will add overhead to the culling and scene graph systems.
Multiple systems will have a higher script cost if you are manipulating them in your scripts.
It depends how exactly you split it up. Imagine the extreme case of 1,000 systems emitting 1 particle, vs 1 system emitting 1,000 particles. Obviously this is a terrible idea but hopefully it gives you the idea that there may be a “sweet spot” somewhere in the middle.
Bottom line: profile it
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