1. M-bus - a sufficient level, and other protocols(logical, phisical).
2. PCB - is very good.
3. MySQL or MongoDb - for your application, it is sufficient to use only several methods.
4. Linux - I'm not a user, but the tune kernel, and the adaptation of TFT driver compiled. The level - preparedness for needed.
5. Charts - it's probably on the basis of ready-made libraries.
6. HTMl, Nodejs, php, and Javascript - experience is present,the level of ready-to-use.
7. ESP8266 - high/low level (in practice, near RF-layer, the MTU packet processing directly), I know about possible problems and how to cope with them.
8. Integrated approach, brainstorming, and others.