But a new question arose: in what format is the electrum wallet created? In the type column, it is only indicated that this is a file. No mention of format.
It's a json file, but that's essentially a clear text file that's organized in a specific order. Electrum doesn't care what file extension is applied to the file, as long as the data is organized in json format. The wallet file could have no extension, a .txt extension, a .json extension, or make up your own. It doesn't matter.
If the Electrum wallet file is password protected and encrypted which should be the default, then it is an text file that looks like ASCII garbage.
If it's only password protected but not encrypted then you will see a JSON text file where the sensitive parts (seed recovery words and extended private key) are encrypted and not directly readable.
When you remove the password protection (not recommend, do this in a secured air-gapped environment!) the wallet file will have all its glory exposed as JSON text file.