They do operate as node points, so they do expand your 6lowpan network and increase the accuracy of the PTag.
Switches are a problem. If the switch is in the off position then the bulb will get the message once it is turned back on but can not defy the physics of an off switch. There are Z-wave switches you can add behind your switches for these use cases.
I am testing 3 bulbs in my house and our Alexa integration. For these 3 bulbs I have completely ditched the switch and just use voice.
However, we have a few ideas to get around some of the switch issues in the future, however that is a long way out.