FM aficionado here
It’s most definitely the OPL3 chip, which was used on the Soundblaster 16 soundcards. The parameters and available waveforms are identical to what the chip has to offer. OPL3 is actually a favorite of mine, it has a really nice crunchy character and Yamaha condensed the FM controls quite well.
As for the drums mentioned, the OPL3 has a drum mode which is most likely what this machine incorporates as well. The drums are quite dinky but charming.
If you want to get an idea of how it sounds like I recommend checking out Adlibtracker 2 or DiscoDSP’s VST emulation.