It’s hard to tell what you’re missing without knowing more details about what you’re trying to accomplish. Most of the hardware that you listed will not work with SmartThings. So it’s more a matter of identifying the specific problems that you’re trying to solve and then looking at what the best devices might be for that.
The Leviton Z wave switches are good switches and they’re on the official “works with SmartThings list,” so that’s generally a good choice. They are more expensive than some other zwave brands, but if you’re getting a discount then that won’t be a factor.
The following thread has some discussions on features by device class. You may not need it but here it is:
When you have a three-way switch set up, you do need to replace all of the switches, not just the master.
You can use an unofficial method to integrate nest products, but you should be aware that in the past, some custom methods have been a violation of your nest terms of service, so SmartThings can’t officially recommend that you do that.
I could be wrong but i’m pretty sure Nest Manager stays within the confines of the ToS as we use the official API, we immediately de-authorize the token then overwrite the data on the ST platform before we uninstall and are not emulating an iPhone to access nest.
Also seeing as we have over 2000+ users currently using the software If Nest had a problem they would have shut us down by now
As far as the number of users, you never know when they’re going to get around to it. Look at what happened with MyQ. That was up for I think almost 2 years before Chamberlain shut it down.