What are the solutions (hardware and software) for organizing remote control of equipment?

Question

Electronics

A task from the field of smart homes, IoT and the like. The bottom line: there are many remote objects with equipment that need to be controlled. Management is implied through the Internet site - the user presses one of several buttons on the page of a particular object and the web server sends a command to the object computer (controller or gateway, I have not fully figured out these differences in IoT terms). Commands run action scripts on the Gateway with multiple devices. The Gateway sends to the Server information about the states, start and end of commands.
Locally, the object consists of several sensors (temperature, humidity, reed switches, etc.), metering devices and actuators (relays), electromagnetic locks, electrovalves, servo drives, etc.
Questions:
I). Which Local Head Unit (Gateway) to choose - 1/ based on MK, 2/ ready-made Mini-PCs (RaspberryPI, OrangePI, etc.), 3/ PLC or smart home controller type, 4/ well, or something that I haven't seen it yet.
II) How to provide Communication or data transfer between Web Server and Gateway? Physically I understand there is a gsm/gprs modem. But at the level of protocols and software, what are the options?
III) What specialist to start with: Gateway specialist (electronics), Web Server specialist (backend), Website development? And how to make them all friends? They say there are software architects, maybe such a specialist is needed?
Additions:
- All calculations on the Server on the Internet;
- After answering and smoking the topic, it becomes clear that you still need a device with brains for normal interaction with the server (not a PLC or an MC), but then I simplify the question:
If the Gateway is a regular PC or a Mini-PC like Raspbery, then in what ways it is possible to ensure its constant connection with the Server, more precisely, what options and technologies are there (at the level of my knowledge, I imagine either a static IP for each Gateway so that the Server can access the address, or the Gateway is constantly connected somehow to the web server)?
Are there architects of such systems here, or where to look for performers?

Answer 1

https://github.com/topics/home-assistant
see what is already in the theme for smart homes.
I recently fiddled with such a thing https://aliexpress.ru/item/4000631637868.html
The bottom line is this. The switch is initialized with the name of the Wi-Fi network and the password for it.
He himself goes to the cloud for commands.
For 700 bucks a year, the Chinese sell a key for an application so that you can use the cloud.
This is for developers of their systems. Simple customer can download the eWelink App

Answer 2

Gateway - or ready with alik and raspberry pi.
The static is unnecessary if the connection will initialize and maintain the gateway >>(to) the cloud. making a constant poll of the server center

Answer 3

It is necessary to clarify in your problem statement what level of remote control do you mean?
Remote control, i.e. remote or you need a fully functional automated control system with telemetry, etc.
The topic is very deep and cannot be discussed in the volume of the sandbox habr.
If you want, let's start a dialogue with the consideration of your idea,
let us know your email.
To connect, google beeptoolkit
https://youtu.be/hXbNbJ49E9w