The Maglev train may be very fast, but it only runs every 30 minutes or once
every hour. ( Sorry, I don't recall the exact figure)
If you just miss one, it's a long wait till the next, such that the regular subway may be faster.

That said, I personally don't believe that 5 hours is sufficient to clear
immigration ( especially the transit without visa rigamarole), reclaim bags,
go into town, come back, recheck, re-do security and immigration.

It often takes well over 1.5 hours to get bags and clear incoming immigration.

I would just stay in the airport.