I could swear that in the past there was some config setting which disabled explosions (such as the ones seen after a panzerfaust missile explodes or the airstrike hits the ground) and only left these "debris tracers". I tried googling it, but it only returned a cvar cg_wolfparticles which does not seem to remove explosions.
Is there a setting like that in vanilla ET or ET Legacy?

cg_wolfparticles, AFAIK, not part of ET:L.
Replaced with cg_visualEffects, I think.
You can't remove explosions (?).
And fair game for everyone :)