Chapell, who spent the final five weeks of last season on loan at Plainmoor, joins on a two-year contract after being released by Sheffield United.
The 21-year-old tweeted: "New chapter about to begin for me at torquay united fc. Can't wait for the season to start now."
Cameron, 20, has also put pen to paper on a two-year deal. He joins the Gulls on a free transfer from Aston Villa.