Yes. If it cant comfortably do more than 60fps, then it wont be able to v-sync at 60fps all the time. If it can only just do 60fps then there will be dips and drops.
I wouldn't say pointless, but it stops visual tearing from being noticed. The idea is not to drop below 60fps, what is over is neither here or there with v-sync on because refresh rate is now locked to frame rate.
Yes. If it cant comfortably do more than 60fps, then it wont be able to v-sync at 60fps all the time. If it can only just do 60fps then there will be dips and drops.