I use in most of my old game machines a EWS64XL with a MIDI daughterboard and a GUS / GUS PnP /ArGUS in the same system. There is no TSR needed.
There are three main points to consider:
The most important thing for first putting in a EWS64XL is checking the resources with the EPROM tool and change it on demand.
The circumvention of the external wavetable mute bug by using CS32MIX (also means internal wavetable here)
The correct setting of the MIDI effects in the TTM file as the default TTM file has no effects enabled at all, which makes the card sound completely dry.
Everything else is straightforward.
Noteworthy is that in Win you can load multiple soundfonts, e.g. a separate one for drums, whereas EWSINIT allows to load only one at a time.
My typical configuration is:
EWS64XL Codec at A220 I5 D1, Dream aka MIDI-1 at A300 I9, external midi aka front panel aka MIDI-2 A330 no IRQ
GUS at A220 I7 I7 D7 D7
depending on the midi device fokus it is also possible to exchange the 330 / 300 ports between MIDI-1 and MIDI-2.
Some Boards use IRQ9 for SMI, then I change the MIDI-1 IRQ to 7. The case for digital playback on GUS in parallel with MIDI playback through the Dream that is actually using the MIDI IRQ as well realisticaly never happens.