No, Voodoo1 was not available to the consumers in an SLI config. There were probably some Quantum3D "single board SLI boards" for Voodoo1 though...not available to consumers.
All consumer Voodoo1 configs (Orchid Righteous 3D, Diamond Monster 3D) were 45 Mhz, 1 PixelFX chip, 1 Texel FX chip. (1 pixel pipe, 1 TMU per pipe.)
Voodoo2 was 90 Mhz, 1 Pixel FX chip, and 2 Texel FX chips. (1 pixel pipe, 2 TMUS per pipe).
So theoretically, Voodoo2 was 4X the speed on Voodoo Graphics in dual texture situations, and Voodoo2 SLI was 8X the speed.
EDIT: Note, comparison of Voodoo Graphics to V2 SLI is not entirely fair: Voodoo Graphics debuted at $300 MSRP...and V2 SLI debuted at $600 ($300 per card)....twice the price. So a comparison of "dollar for dollar" between generations puts V2 SLI at about 4X the performance in ideal, dual texturing situations.
In practice, it was difficult to demonstrate the realization of this difference in terms of FPS...because Voodoo Graphics boards only came with enough memory (2 MB Frame buffer) for 640x480 resolution....and with Voodoo2 SLI, 1024x768 was possible...one of the V2 SLI selling points, btw. (So you could never run 1024x768 on Voodoo Graphics for a direct fill-rate limitation comparison...)