I did some perf tweaks on my stream machine (7945HX) and now it comfortably runs one VTube Studio + OBS.
2x VTS (for me and Cyan) also holds 60FPS... if I turn Chroma Key off. So hopefully once the Spout2 stuff is sorted I'll be good!
(Or I could just throw a dGPU in there... there's a slot ^^)
I think it's mostly fill rate/bandwidth bound, overclocking the memory a bit helped noticeably.