Particle systems question

Hi, I have a theoretical question regarding the best use of particle systems.

I want the player to be able to trigger weather particle effects to start - rain, snow etc on the level when I want.

Is the best way to achieve this in terms of minimal processing etc - to attach the particle emmiter to the player character above and have it follow them around, only
turning on and off when I want in the blueprint and keeping the particle box quite small to give the illusion of rain everywhere or,
have the particle emmiter the size of the total area where rain would be required and switch visibility on/off as needed. What is the most efficient way to achieve this?

Also, when an emitter is emmitting particles does it only affect performance when the actual particles are visible or is it best to have them not emmitting even when not visible?.

Hope this makes sense!

Thanks in adv

It is better to use an emitter following the player and activating/deactivating it whenever needed. Also use GPU particles whenever possible. You can have more particles with less performance cost.