CMOS Inverter design
in my opinion,normally the propagation delay and the rise/fall time are two parameters that have no directly relation, the propagation delay is for speed, while the rise/fall time is for signal quality, that the propagation delay is bad does not mean the rise/fall time is bad.
but for inverter, it is true, if the width of pmos is bigger, the rise time would be shorter and the output rise propagation delay would be smaller, the same is for nmos
Added after 7 minutes:
in addition, i guess the rise/fall time you mentioned is the output rise/fall time,
as for input slope( or rise/fall time), the propagation delay and the rise/fall time all depend on the input slope