I had the exact same combination when Voodoo2 and TNT2 Ultra was some of the best cards you could have.

The TNT2 gives much better image quality and the Voodoo2 great performance in games with Glide support. So its the best combination from two worlds.

In most games you can select if you want to run OpenGL, D3D or Glide and it will chose the correct card from that.

It’s a almost perfect setup, used it back in the day and have an almost identical setup in my P2 rig.

Glide games will run via the Voodoo2 and OpenGL will default to the tnt2 unless you use a Glide Gl mini DLL.
The Voodoo2 doesn’t support OpenGL without the mini Gl DLL which makes it pretty simple to know which card the game will use.

Direct X will require a little tweaking by disabling direct3d in the Voodoo2 control panel after which any D3d games will use the TnT2.

Some games also let you select which card and api you want to use but D3d via the Voodoo2 isn’t great and image quality is also middling.

The main reason for pairing a Voodoo2 with a TNT2 card is for Glide support.

Seeing the 3dfx splash screen is the easiest way to tell if the Voodoo2 card is running and using the Glide renderer.

With OpenGL, it will use the nVidia ICD by default unless a 3dfx miniGL DLL is in the game directory or playing Quake 2 which has an OpenGL option specific for early Voodoo cards.

In games that uses the D3D renderer, the Voodoo2 card gets always treated as a secondary adapter, but earlier games tend to prioritize it over the nVidia card. This behavior can be disabled with some tweaking and third-party utilities.

Understood. Thanks

Let's say I wanted to use a Voodoo3 instead. No pass through here.
Would a VGA switch box work? (TNT in - Voodoo in --> Active VGA out)

If I wanted complete control of course yeah I could disable whatever card I don't want and physically connect whatever card I want at any given time since V3 can do 2d. However that kind of defeats the convenience factor.

If the Voodoo3 card is the PCI version, yes. Setting which one would be the primary display card depends on the BIOS setting.