We're planning to put R60 cellulose insulation and a radiant barrier foil. We will staple those barriers into the roof framing. Will the radiant barrier foil withhold an R60 insulation to prevent it from going to the soffits or we will still need to install PVC baffles?
As was implied by the clarifying questions posed in comments, this depends entirely on what the product you mentioned actually is. Mylar and similar films tear very easily, so if it doesn't have reinforcing strands or a more robust backing it's likely to fail as an insulation support where small tears exist from fastening. I would consider installing the baffles upside down so that the flat panel supports the foil.
That said, once insulation is blown it doesn't move much, and all weight is away from the baffles. Gusty winds can shift the top layer a bit, but eventually it settles in and stays put due to additives and the binding nature of insulation fibers. So you don't need a lot of strength to do the job.