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.
The way bech32 is designed is to make the address standard unambiguous. Those lookalike letters have already been eliminated and standardizing all of the characters to either be in uppercase or lowercase will reduce the chances of typos.
There is absolutely nothing wrong with representing them in uppercase. Wallets like Electrum will automatically convert it back into a lowercase string if you enter an address in uppercase. AFAICT, some wallets like Electrum represents bech32 addresses in lowercase; nothing wrong just that not all follows the recommendation.