Great Review, thanks for the detailed info after spending some time with it.
Gate - Noise Gate, silence any hissing
EFX - GEQ maybe?
Amp - Amp Sim?
IR - Cab Sim?
Mod - Chorus or Phaser or Flanger maybe?
Other then the Gate, just guesses. EFX could maybe be distortion or fuzz instead of EQ, but I can’t say without playing with it.
That is all pretty decent for a little headphone amp.
I mean, it is no DarkGlass, and it is not the Boss or Ashdown or ?? a few others that make little headphone pre-amp / amps. But it seems to be built to be a lower cost alternative to get you some of the features those others are offering.