OWB on Pegasos 2 g3@600 is even worse and forget about youtube it's like watching a slide show.
Not if you're using a non embedded video replay mode (i.e. overlay full screen playback) - then youtube is fine even on the Peg1 and nearly fine on Efika (the low Ram spoils it more severely there).
Anyway, rich web content requires some cpu power of course. And while I know that the lower spec computers can be pretty useful with MorphOS, I prefer my beefier machines by far.