^ Hi glad you are enjoying the mod. No worries on the modding questions I don't mind.
The particles are indeed typically resized for fighter weapons, though not in all cases. Mostly in the ones that would be more noticeable. On the technical side: they are separate weapon files from the ship-based ones so they can have separate projectile files as well, or in the case of beams I can just make the particles smaller in the weapon file itself.
As a side note, I think they may be slightly reduced in size by default as well. It at least certainly seems that way for missiles and torpedoes.
As far as the weapon sprites getting shrunk down.. I wish there was an easy answer here- such as simply putting the weapon sprite components in paint and reducing image size by 50% or something - but they are actually all custom drawn (I use paint.net) and kitbashed from existing weapons. Reducing size often makes the image quite blurry.
What I do:
I spend some time looking at the weapon I want to shrink to see what detail would be impossible to reproduce in a smaller form (so I know to ignore it when kitbashing or paint over it) then try and get a good idea of the weapon sprite's "shell" and basic features. At that point if I can use bits of the original weapon for kitbashing I do. Sometimes I take 15 or more tiny pieces to create the form and then blend/erase them using colors taken from the original until it looks right. Sometimes it just takes 2 or 3 pieces.
There are also instances where I had a small version of the weapon that fits the medium weapon size well enough to use that sprite. Its different case by case.