Train ride BJ - Hong Kong with 144-Hour Visa-Free Transit

Hello,
we would like to travel from BJ to Hongkong by train. We will enter China arriving from Japan by air. After some days in BJ we want to leave China by using train to Hongkong. We will not have visa, because we want to use the 144 hour Visa-free-transit.
Can we use the High speed train for this ride? Or only the overnight train?
Thank you