I guess this is a trade off that depends on your use case: from which distance does the qr code need to be scannable, what cameras do we expect to be used for scanning, how likely is what kind of damage to parts of the qr code, ...
Indeed.
The local bus transit has a digital ticket system with QR codes for tickets. I haven't actually tried decoding the codes but just seeing them and interacting with them I can tell they have gone WAY overboard with either the amount of data they try to fit or the amount of error correction. Probably both. They are nearly unscannable due to their size and all the bus drivers just wave you along if you don't manage to scan it.
