Are they compatible (cheap Chinese WiFi devices in general)

I am certain this has been discussed but are Chinese Off brands on amazon compatible with STv2 hub. Examples below. But in summary, I have swaths of things like light switches and contact sensors, bulbs and power outlets that work on the smartlife platform. I’d like to integrate them into my home control hub’ish Fire tab8 running action tiles via smartthings. Currently they work very well with Alexa but central control at the panel would be ideal

Generally speaking, no. Most WiFi only devices aren’t compatible with ST without a device handler. Even then, it’s basically a crap shoot guessing which company will write (or promote the writing of) compatible device handlers. That’s not to say it’s impossible, but rarely are such off-brand devices supported on ST.

As @Core_Phx mentioned, there is no one way to do this. It depends very much on the specific brand and model and what that manufacturer has implemented as far as integration options.

For example, at least one of the devices that you list uses the Tuya SmartLife app, and there is a limited integration with those.

See the FAQ ( this is a clickable link)

FAQ: WIFI Devices in ST? How can I integrate a WiFi device that isn’t on the official compatibility list?

This is the officially supported list

Unless you want to code your own device type… this is the best place to start.