Yes, this question gets asked often for various permutations of sound cards.
You could just not run the hardware wizard to detect the ISA card in Win98, or disable it in the device manager.
You might also be able to only make the OPL2 active in Win98 and then get the games to use that instead of the Vibra's OPL emulation but I don't have any experience with that.

This essential how I've now gone about it

My 98 rig's got an AWE64 Gold and an Audigy 2 ZS. I use the Gold for Dos games and MIDI usage in Windows and the ZS for Windows games. Gold's outputs are routed into the ZS's Line in, CD Audio's connected into the Gold, the ZS is the primary output and input device. Using the VXD driver for the ZS and the whole thing works great.

Sounds pretty cool mastergamma12. I had the VIBRA 128 install ok in Win98 and assigned itself A220 I7 D1 for Legacy mode all ok. I set the jumpers on the SB 1.5 for standard A220 I5 D1. I was already booting Win98 from an SD/IDE adapter with an old 2GB HDD Formatted FAT16 with DOS 6.22 with booting from floppy into DOS 6.22. Older Dos Games for OPL2 working great booting into DOS 6.22. I configured the VIBRA128 Dos Drivers in the Win98 Autoexec no problems and turned the boot menu on for Win98 so can go straight to DOS7 for later DOS games to use wavetable midi. I'm doing 2 sound cards in another machine now (Athlon64) with a Yamaha YMF744 for Win98 and SB X-Fi XtremeGamer for Vista (If I could get XP SP3 activated I'd rather use that)

There is a way to save a configuration in device manager. When booting, all of your configurations will be presented too you and you can select one from a list. I have used it before as an easy way to manage three sound cards before. Each profile has one sound card enabled with the other two disabled.