Enhanced Effects(cg_enhancedEffects/Setup Menu setting) were something introduced as part of B19.0, and tend to be the most frequently-neglected but most visually-impressive feature of MBII content. Including enhanced effects support with your creations can make a world of difference in how they're presented to players.
Enhanced Effects in general won't be covered here, just how they relate to third party content such as FA configurations for maps, and new vehicles. First, in Weapon Overrides in FA files, there are a few effects values that allow for the defining of enhanced effects with custom content, namely:
Note that only the non-enhanced version of an effect is required to exist; Enhanced1 and Enhanced2 effects are optional. That is to say, the actual .efx files that create the visual/audio effects themselves are optional, but even if you don't plan to use them, if you're using a feature that supports Enhanced Effects, you should always include the effects values in the FA files, even if they point to a nonexistent .efx file. That's part of the beauty of Enhanced Effects: If someone's trying to use Enhanced2, and that efx doesn't exist, MBII will attempt to display Enhanced1...and if that doesn't exist, it'll fall back to the normal, un-enhanced effects.
Not quite as obvious, there is also Enhanced Effects support for vehicles, through effects values in the .vwp(Vehicle Weapon) files. Take an excerpt from droideka_laser.vwp, the Vehicle Weapon for the Droideka in MBII:
impactFX "vehicles/droideka/droideka_blasterhit" impactFXEnhanced1 "vehicles/droideka/droideka_blasterhit_enhanced1" impactFXEnhanced2 "vehicles/droideka/droideka_blasterhit_enhanced2"
Likewise, we have some text from atst_laser.vwp:
impactFX "atst/wall_impact" impactFXEnhanced1 "atst/wall_impact_enhanced1" impactFXEnhanced2 "atst/wall_impact_enhanced2"
impactFX is the effects that will be played with Enhanced Effects set to low, or if Enhanced1 or Enhanced2 effects haven't been provided. impactFXEnhanced1 and impactFXEnhanced2 are the effects values that point MBII to .efx files to use for the medium and high settings of Enhanced Effects. You should always have these setup in your .vwp files if you're using impactFX at all, even if you don't have an .efx file for them to use.
As a general rule of style, un-enhanced MBII effects should be fairly bland, and performance-conscious: they shouldn't look out of place in BaseJKA. Enhanced1 effects usually tend to be a bit smoky, or include rarely used but potentially performance-impacting effects. Enhanced2 effects are meant to be over the top, high quality effects that dazzle the eyes and ears. Blinding flashes, sparks and flames grouting across corridors are not out of place with Enhanced2.