All games use mailbox/triple buffering. Except when you enable sync to
host refresh, in which case FIFO/double buffering is used.
This means vsync enabled will ever tear, but at the same time, never
drop to 30fps on a missed frame due to frame rate differences.
To have the "best of both worlds", you should enable vsync and sync to
host refresh. Previously, this resulted in additional input lag, since
the host vsync would drive the EE frame timing. Now, this behaviour is
disabled by default, unless you enable "Use Host VSync Timing".