There is a zone expander that works with both the IQ Pro and the IQ Hardwire PowerG so you can add more wired zones if you want.
Wired is generally considered to be the most secure and reliable but PowerG is pretty close. Some people are die hard for fully wired. Wired can be harder to install though.
If you already have a bunch of working wired sensors then you would probably save money using them vs replacing them all with new wireless sensors.