Intel Extreme-GFX were the old igp's Extreme-GFX 1+2. All I can tell you about it, that i865gv and perhaps 845gv do support the DX7 effects in O.D.S.M. (former intel-igp's do not!) and you can benefit from stutterfree-scrolling in JazzJackRabbit2 (Hardware-Mode) with 640x400@8Bit. The 865gv is a very good chip!
With a capable P4 you get decent performance in D3D and OGL up to 800x600 40+fps...and you can use the early texture-compressions DXTx which looks very nice in unreal and ut99 and soldier of fortune1
Retro-Gamer 😀PowerMac 6100-66/Houdini 486/66 - G4 Cube 450/Rage128pro OS9.0.1 - Macintosh LC/Apple IIe Card OS6.0.8 - Acorn A4000 Archimedes - Unisys CWD 486/66 + Aztech Washington