An easy but possibly very important tip: If you use only UPPER CASE alpha and numbers in codex32, and avoid most punctuation, it makes QR rendering of it significantly smaller. This is because the QR code to the ISO SPEC, when seeing lowercase, assumes the value is binary, then converts it to a two byte value. If instead, the codex32 is all upper, and it uses only the 45 allowed characters (see https://www.thonky.com/qr-code-tutorial/alphanumeric-table) , it will leave it single byte and try to compress it. Of course it doesn’t compress well, but that is OK because it at least didn’t double the size first.
See our research on this topic at https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-003-uri-binary-compatibility.md A superior QR codec can do better (see our https://github.com/BlockchainCommons/QRCodeGenerator or https://www.nayuki.io/page/qr-code-generator-library) but many platforms and more basic QR codecs will double the size of the QR if you have any lower case. — Christopher Allen
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