They were stored as integers. All samplers sample and store as integers. Computers sample and store as integers.
The samplers you mentions all had CPUs with 32-bit processing, but many of them only had a 16-bit data path (Motorola 68000) and no FPU, so the sounds were processed as integers when on the CPU.
Other operations, such as filtering, were done on dedicated VLSI chips- essentially custom built DSPs. (The notable exception would be the Emax I, which had analog filters). The EPS 16+ could actually load new routines onto its DSPs from disk (Waveboy effects). These chips were 16, 20, or 24-bit depending on the model under discussion. The chips still worked with the sound as integer data, more often than not. Often, the 'filter' chip and the 'effects' chip were separate... Ensoniq recycled their seperate effects chip into effects units.
This is drastically simplified, but that's the gist of it.