My experience:
I have a 718C with the standard suspension, standard seats, 19" wheels and PDK. Previously I drove a vintage Boxster S with PASM. The 718 has a much more compliant ride than the 997 had. My wife and I find it quite comfortable on smooth roads but it still provides the handling required for spirited driving. As far as seat comfort goes we are very pleased. My wife has back issues and she has suffered in virtually every car we've had in the last 10 years. She, as do I, have found the seats quite comfortable even after a day trip of 6 hours ( 3 hours each way with a couple of hours in between).
There is a bump on a road near my house that would bounce the 997 off the road at 30 mph, but the Cayman just swallows it up without losing composure.