As a former network engineer myself, I tend to implement slowly. I started with a zwave doorlock and one zigbee motion sensor for the first few weeks, just testing system reliability and looking for sources of interference. But that’s just a personal preference. Some people prefer to jump in with several dozen devices at once. Your choice.
SWITCHES AND DIMMERS
I personally prefer light switches that have what is called “instant status” capability. But those are a lot more expensive than the kind that don’t, like $45/switch vs $25. So I tend to get Leviton or Cooper in models with that feature, rather than Linear or GE/Jasco. But it’s not worth the markup price to everyone.
The Aeotec micro relays and micro dimmers (which also support instant status) let you keep your existing switches (they install inside the switch box), which a lot of people like in terms of decor. The wiring is trickier than with the other brands, though.
On the other hand, my house was built in the 1950s with archaic wiring, so my preference isn’t always possible, and I often end up using either plug ins or battery operated switches instead of replacing a wallswitch.
One caveat: if you want a lightswitch to act as a zwave repeater to a doorlock, it needs to also support “beaming.” (Most Aeotec and Jasco models do, but check to be sure.)
Zigbee sensors will tend to have somewhat better battery life than zwave, and I hate changing batteries, so that factors into my choice of small sensors.
For the glass door sensor, it just depends. Those get broken less often than regular windows because they tend to be sturdier and, to be honest, pretty easy to open. So I would myself more likely use multiple motion detectors in a zone pattern in that room. But that usually doesn’t work if you have pets.
THE OFFICIAL “WORKS WITH” LIST
If you get products on the official “works with SmartThings” list then support will be able to give you more help if you run into any issues.
Just make sure you read the little “I” popup on the list if there is one, not all devices are fully supported.
And “SmartThings Labs” means in beta.