As far as your current devices…
.1. Nest thermostat There is no official integration with nest thermostat. There is an unofficial integration which is quite popular but is actually a violation of the terms of service of your nest account. So the official support article says you’re choosing to use it at your own risk.
https://support.smartthings.com/hc/en-us/articles/204733384-Does-SmartThings-work-with-Nest-
.2. I don’t think there’s any integration with nest cam except through IFTTT, Which is one way only, but hopefully others will know. You wouldn’t be able to view video in Smart Home Monitor because that is limited to a few specific cameras, but you might be able to get stills. @smart or @pstuart might be able to say more.
https://support.smartthings.com/hc/en-us/articles/205380804-Video-integration-with-Hub-v2-FAQ
.3. Phillips Hues have been working pretty well, but the integration broke for some members last week. Engineering is working on getting it fixed again. It does still work for some other members so I’m not sure what the difference is.
.4. I believe the LIFX integration is working. You will need to use custom code to get Group control.
https://support.smartthings.com/hc/en-us/articles/205956530-LIFX-light-bulbs
.5. Chamberlain is complicated. There is no official integration at this time. There was an unofficial integration which, like nest, violated the terms of service of those accounts and Chamberlain eventually shut that down about two months ago. There is currently an alternative unofficial method. It doesn’t have as many features as the old version, and you will have to buy an additional tilt sensor device to make it work. It also cannot control the lights on the Chamberlain. So it meet the needs of some people and not others.