My recollection is that the 1100s were the worst bouncers in the tunnel. Felt like they'd come off the track at any moment. The early 10s (the converted double-enders; everything was single-end in the 1960s) were better, and the newer 10s (the last streetcars Muni bought) were quite smooth. So the track certainly contributed, but the car design (probably the truck design) had a lot to do with it.

The iron monsters were probably fine. I never rode one through the tunnel. But they were slow and very heavy so they probably wouldn't get into that resonance range where bouncing serious bouncing happened.