Lowes has two sensors of the Iris window sensor and motion sensors, but not sure which ones work with ST v2?
lowes.com/pd/Iris-1-Sensor-Indoor-Door-and-Window-Sensor/3735305
https://www.lowes.com/pd/Iris-Motion-Sensor-Works-with-Iris/999925310
And are Iris still considered a good alternative to Fibaro, Ecolink, Aeotec? I read some reviews that the Iris’ battery life is not that great.
These are great sensors, and I have tons of them - 58 of the open/close sensors, and 29 motion sensors. Battery life for me has been excellent.
The ones in the purple packaging work with ST, but not the ones in the blister packaging.
These work with ST:
http://www.lowes.com/pd/Iris-Contact-Sensor-Works-with-Iris/999925302
https://www.lowes.com/pd/Iris-Motion-Sensor-Works-with-Iris/999925310
These do NOT work with ST:
https://www.lowes.com/pd/Iris-1-Sensor-Indoor-Door-and-Window-Sensor/3735305
https://www.lowes.com/pd/Iris-120-Degree-Passive-Infrared-Security-Motion-Detector-Works-with-Iris/1000008670
Iris’s latest smartplug and water leak sensor also work with ST.
Thank you.
Does it make a difference if most of the other sensors are Z-Wave?
None whatsoever. I have a large mix of zwave, zigbee, and wifi devices all working great together.
I do recommend adding a few of those Iris SmartPlugs around the house because they act as both zigbee and zwave routers, and it WILL make a difference (even with ST branded devices), especially if you don’t have any mains powered zigbee devices in your home. I have several of those too 
or should I look for others?
Those are OK, and there are a few discussions in the Community about them. I personally don’t own any, so I can’t comment other than from what I’ve read. All I’ve ever seen is that they can be a bit flaky with ST. They are wifi and don’t provide any routing capabilities for zigbee/zwave mesh HA networks.
Personally I’d look for other devices in the zwave/zigbee space.
Using Iris-branded ones?
If you’re looking for wall plugs. then I’d definitely recommend the Iris device:
https://www.lowes.com/pd/Iris-120-Volt-White-Smart-Plug/999925330
But not this Iris branded device (it’s wifi only)
https://www.lowes.com/pd/Swann-120-Volt-White-Smart-Plug/1000135207
The reason why I like it is because it’s both a zigbee (by default) and zwave repeater (if you need it, but requires a little more set up). There’s a Community discussion about these devices that you can read that talks more about the zwave set up.
It also reports power consumption, so I have these on my TV’s, projector, audio devices, and a couple small bar frigs.