Does anyone have any non gimmicky smart home stuff implemented at home?

I am not sure what you mean by non gimmicky but @loud-glass-33663 had some good recommendations here. I bought these plugs and have set up automated routines https://remoteindian.slack.com/archives/CFKUPJZ7W/p1618125743236400?thread_ts=1618122867.232700&cid=CFKUPJZ7W

Is the IR blaster approach better or the smart plug approach?

IR blaster works for things like AC and TVs — so depends on what you want to use it for. If it can be controlled by a remote control, good chance IR blaster will support it. But for stuff like lamps, etc. you will need the smart plug or a direct wifi bulb.

Anyone done things with CO2 sensor and if it is high indicate with a red light (for example) kind of stuff?

You’d be hard pressed to find niche stuff like CO2 sensors which work out of the box and connect to the internet in India. I tried doing a cursory search and this was the best one I found — which does not connect to the cloud. Unless of course you are going to buy parts and do some Raspberry Pi hacking 🙂 I have an IFTTT and along with Wyze door sensors, have set it up so that one of living room lights come on if door is open between 6PM and 8AM. It works fairly well. A gimmicy thing I have done as well is to have my phillips hue light blink when the ISS passes over it. (It works very well). IFTTT also gives you web hooks, so you can fire CURL commands from your computer and get stuff done like turn on and off lights in another room, etc.

Thanks @loud-glass-33663 for the details