I have Unisound configuring dual sounds cards on my 486 under DOS. I have an SB16 Vibra and YMF719-B. The SB is the main card with a short audio cable from the YMF's unamped out to the SB's line in. The SB handles digital audio and game port, the YMF handles OPL and external MIDI. It's possible to create batch files to switch on the fly to have ADLIB handled by the SB for those few games that don't work on the YMF.
To configure this you need to set blaster for the resources of one card and then run UNISOUND with a -c <cardindex>, then change the blaster variable to the other card's settings and run UNISOUND again. Finally set the blaster one last time with the full list of ports that games will use to config themselves.
EDIT: Also, while it was tricky, you don't need to give a card a configuration for every resource. I believe you can set something to 0 in the set blaster variable and it won't initialize on the card. I don't have the MPU401 or ADLIB defined on the SB, and I don't have the SBPro or gameport configured on the YMF.