But... As soon as your bridge for the lights is on some sort of guest AP/network, your client on your phone can't reach it anymore, and thus has to be on that same network. And that will annoy you quick enought to not try to install the extra or guest AP at all...
Depends on the IoT device, some only have web interface that is controlled via manufacturers website, so as long as the actual device has internet connectivity you can do everything. Or maybe you can setup a "thorwaway" PC as a sort of proxy? Or maybe just one of the old (and sad) tablets/phones, depends on what you need/want to do and what kind of interfaces your IoT devices offer
Using a device that is controlled by an external "cloud" server is even worse - you've just given an untrusted 3rd party root access to a device on your lan.
Plus, devices like that are almost guaranteed to become garbage very rapidly when the vendor decides to stop operating that central command server, wherever it is. And unless you're paying a maintenance fee, they're going to cut that off pretty quickly once they stop selling new units of that particular model.
It's the biggest reason why I'm skeptical about all things IoT: too much "cloud" without an SLA or any guarantee of longevity on the service side.
Just as dumb as 2000 mile data path to a doorbell or security camera, but that still exists.
I personally haven't really thought about getting a IoT light bulb, but I would imagine you would program them to turn on when sun goes down, that shouldn't need direct connectivity and the bulbs can't tracks your phone moving aruond the house (or at least I doubt they can), so you either have to turn them on with your phone as you move along or just flip the switch or install actual movement sensors.
I'm probably completely missing the point of smart light bulbs, maybe you have actual use cases?
