There is not really a way to disable special effects or tune the quality down AFAIK.

Modding may be the best course, though the setting option presented might help you some too (most people increase this though .

If it's abilities you could easily replace the lines you think are causing issues with null effects: 

effectInfo
effectAttachInfo
attachType "Invalid"
smallEffectName ""
mediumEffectName ""
largeEffectName ""
soundID ""

If it's explosions you'd have to edit their Explosion def file.

If it's overly complicated weapon hit, travel, etc particles causing the issue... good luck

You could also reduce the number of particles allowed in the rebellion settings file. This would affect all particles but might help your system:

MaxParticleCount 7200
MaxParticleSimulationsCount 2400