No more further explanation that bech32 addresses can either be in capital or small letter, but according to all the wallets I have used before, the bech32 addresses are in small letters and numbers, which should be the recommended way. Some people may want to change it to capital, this might lead to typo error, even if bech32 address can still point out few typo errors, it should not be recommended if the wallet someone is using uses small letter which I believe is the standard wallets are using which makes the QR code have smaller field.