The IQ Panel 4 does have a few more features than the IQ4 Hub. One big difference is the IQ Panel 4 433mhz will be able to handle your existing wireless DSC 433mhz sensors as well as PowerG sensors.
PowerG would have greater signal strength and better encryption. You can find more info on PowerG here
It appears that the requirement for the PowerG recessed sensor is a 3/4 inch hole. This would be a bit bigger than the slightly above 11/16 required by the DW4917. It is very close but it might be a bit to small for the PowerG sensors. You would need a 3/4 inch bit to make it the correct size. Another option would be to abandon the recessed sensors and use the surface mount PG9303 sensors
PowerG has improved range and encryption but you would be able to also use 433mhz sensors.
It would be best to add a door if you think you may leave it accidentally unlocked. A glass break can create an alarm if the glass is broken on both away and stay but a motion would only create the alarm if armed to away. If the door is left unlocked and someone opens it, they would be able to walk in without an alarm being created. If you’re thinking of just using the system when you’re away from home, then the motion and glass break should be enough.