Yes it is, possible but was sometimes buggy or occasionally the cards would have resource conflicts.

Was also possible although more difficult under Windows 95, 3.11 and even dos

CGA/MDA being the first dual monitor configuration

That GT7600 is extremely modern by 98 standards. It's no wonder your running into compatibility issues.
If you wanted to simplify your setup you could try swapping it out for the Radeon and checking how rest of the games perform.
BUT as it's just the one game your having issues with you could go down this dual card option.

As mentioned above, Win98 supports dual screen, It's the video card drivers that cause most issues. My money is Matrox drivers having a better chance playing nice with the Nvidia ones.
You'll also have to switch the primary card in BIOS from AGP to PCI when you want games to use the Matrox. Most games of this era didn't allow you to select which display card was used and would just default to the primary.

GeForce 7600GT is not suitable for Windows 98 as it requires driver that is too new. It's a Windows XP graphics card. You need GeForce 4 or FX.

Yes, I use a AGP Radeon 8500 and a PCI Voodoo 3 in one of my rigs. Just have to switch primary in the BIOS.
Nut agree the Geforce 7600 is going to be problematic at best with Win98.

I don't remember where I found this years ago, but credit goes to Mike Roemer, the author. This is the guide I use to accomplish having two video cards under Win98SE.

It's also available here, although I'm pretty sure this isn't where I originally found the document:
http://www.hellsangels.firstflare.com/documen … lHwProfiles.pdf