I just installed an IQ4 and 2 x PG9WLSHW8 this weekend and the answer is NO, resistors are NOT required.
When defining the sensor, you have “Input Mode” options for “Disabled”, “Normally Open”, “Normally Closed”, “End of Line”, and “Double end of Line”. Setting to “Normally Open” or “Normally Closed” is what you would use if you do not have resistors. Setting “End of Line” or “Double End of Line” would use if you are installing SEOL or DEOL resistors.
When using auto learn or manually adding the zones, they will default to “End of Line” for the Input Mode, so you just need to manually change it if not using a resistor.
I actually have a mix of zones with and without resistors and they all work fine as long as they are properly programmed in the IQ4.
As far as expansion goes, I happened to come across this post this weekend that references a DSC HSM2108 Zone Expander being able to be used (up to 4) with a PG9WLSHW8 but couldn’t find any other details about it specific to Qolsys use: New Equipment Release Dates? (IQ4, POE 4K w/ Audio, PowerG higher limits?)
I actually purchased 2 x PG9WLSHW8 before even thinking about expansion capabilities on a single one so kind of a moot point for me as I won’t need to go beyond 16 wired zones.
As far EOL resistors in general, they should be at the contact side, not the panel side if you want the benefit of what the resistor provides. To meet UL the resistor needs to be at the end of the line not at the panel, but most residential installers don’t care about meeting UL, so it’s easy to place the resistor at the panel if the panel requires one. There’s also the fact that placing a resistor at the contact in a typical residential install using mini reed contacts is just not viable from a packaging/space/aesthetics standpoint, so that’s another reason you generally see the resistor at the panel when it’s required. If the panel doesn’t require a resistor, then no need to even bother unless you want the benefit of the resistor and are installing it in the appropriate location.
GRI makes contacts with built in resistors. I have not used them but I looked into retrofitting my existing contacts and decided against it. The alarm wiring in my home is now 18+ years old and I’ve never had an issue with any of my wires including replacing my windows and re-using existing wires (not contacts though). The GRI ones only cost about $3-4/more over the typical Honeywell/Ademco reed contact and are all SEO. I personally haven’t come across contacts with built in DEOL, but they may exist: