I see there used to be a really cool way to ad light paths or streaks in the particle system but when the particle system was upgraded the option was removed. Does anyone know how to make light streaks using the particle system or possibly geometry nodes and the particle system? I want some of the embers from my fire to have long streaks just like real fires do. Here is an example of what I am trying to acheive:
Hum, to do that with geometry node it’s a bit involved but definitely doable…
But that would mean doing everything within geometry nodes. One way might be to add a bunch of curves that represents the path of embers and use the trim curve node to cut a fraction of the curve.
And obviously use time and offset to create the effect.
Another solution you can try if you’re using cycles is to do it “for real” with motion blur and if the embers move very fast you might get this effect, IIRC I already did something like that a few years back !
Have fun !
Take a look at this geonod asset pack:
https://superhivemarket.com/products/blender-dynamic-vfx---elemental-asset-pack
Some fire simulation setups (especially camp fire) “play” with flying sparks using some particle system with a collectionof different spark shapes and using some wind (sometimes the same as used for the fire sim) and also for exampe vortex..
I haven’t played with something like “particle afterlife” or whatever it is called used in some “wavy swirling streak animations”.. (some "only use curves to follow) so you may also get some inspiration from that (if they use particles 
).
Maybe the first mentioned particles can also be used when also rendereing a vector path and use this for some postproduction, because in fact this is some “analog film expose effect”.
You might want to take a look at this demo file. It covers most things you would need when using a particle system.
HERE Ember Forest by Mike Pan
Since it is an older EeVee file, you need to add a Glare filter > Bloom in the compositor to get the original effect.