Since I have the master files for SQ1VGA's SFX, I can tell you:
- there's 49 digital sound effects, at least in the master collection. I haven't gone through them all to see if any are unused, dupes etc
- there seems to be 36 digital sound effects in my in-game records
- the original file format of the digital FX was SMP, which was changed to WAV and then compressed with an equivalent MIDI using Sierra's SND format, similar to how the game's Roland MT-32 and other MIDI files (MIDI->SND in that case, for effects SMP->WAV, then WAV+MIDI->SND). For those players not using SB effects, a MIDI version was made, although sometimes a blank/dummy MIDI file was used for effects using vocal samples like Roger screaming.
The game was composed both musically and effect-wise for the Roland MT-32, with digital audio sounds added late - one timestamp shows the same month as the game release, and most were finalised in the last 2-3 months.
If there's further questions, or you want a specific sound effect, let me know.