Why the Archeron?  It seems to be more a travel pack than a "hiking" pack though it is clearly a hybrid.  The guide load range is 25# to 45# which is quite low for a 70 liter pack and since it is a ~5#+ pack that tells me it may be oriented towards air travel where the max weight is typically 50#  possibly accounting for its flatter simplified externals.

For wilderness backpacking the Aether or Atmos lines might be better starting points if you like Osprey but it does depend on your plans.  The Archeron may not be that comfortable if you hiking any distance.

Certainly it is hard to pin down a recommended capacity for something as vague as a "5 day hike" since that depends on whether you are camping or staying at hostels and whether the time or location requires special gear.  Winter, altitude, latitude all may require bulky cold weather clothing.

Whatever, I would recommend visiting an REI store or similar and getting fitted.