Varchar storage and performance
I thought in MySql up-to 255 chars with a varchar it is the number of characters you store plus 1 for length. So if you  put a value that's 10 characters long, that'll be 11 bytes on disk.

UPDATE
Found a link to the documentation to back that up. First table demonstrates the difference between char and varchar: https://dev.mysql.com/doc/refman/8.0/en/char.html