Welcome to the MOD.
The JCM800 on the MOD is a striped down version, as already mentioned by @falkTX
This is done because the original was to heavy in CPU usage for the MOD Duo.
I’m pretty sure that the Dwarf will be able to run the original version, which indeed sounds a way better. (The filters been designed for 96kHz samplerate and use a resampler in original to match that, this is removed for the MOD, beside some other strips)
The original version is part of the guitarix package and could be tested under Linux.
Btw. it isn’t to heavy for a usual X86 processor, here it use 5% DSP load.