Here's the most invisible operating mode I've found so far on the FabFilter Pro-L version 2...
“Modern” or “Safe” algorithm
attack max (removes this control from use)
left/right operation unlinked
Ceiling -0.2db (so it doesn't clip when converted to MP3)
Just clip occasional peaks by 1db
Clipper mode removes unnecessary complexity. The limiter just ramps up fast, clips whichever channel peaked, and gets out of the way. No two stage release ("attack" and "release" are actually both release controls, which is confusing). No oversampling, which sounds sort of nasty to me. No stereo linking. Minimalist. Clipping an occasional peak actually sounds more “hi-fi” to me than a bunch of attack/release pumping.
When you engage the audition button (difference between the input minus output) you should hear silence, just an occasional "pop" in one or both speakers as the limiter briefly flicks on. I confirmed that this algorithm is doing nothing while audio is below the limiter's threshold by using SpetraFoo's transfer function; both frequency and phase are flat across the audio spectrum.
From here you can increase the lookahead to avoid harmonic distortion, 3-5ms gives a less crispy high end when the limiter pops. And you can also mess with increasing the release for a less punchy sound, that blends with the track's tempo.
Note there is a preset called "almost clipping" which uses similar settings, but the "Aggressive" algorithm. To me this sounds less transparent than "modern", but might be useful for more aggressive-style electronic music.