I am upgrading a database from 5.7 to 8.0 in MySQL and ran across this: How to easily convert utf8 tables to utf8mb4 in MySQL 5.5
I understand converting the schema and tables to utf8mb4 and utf8mb4_unicode_ci but regarding the changing of columns to varchar(191) I was lost. I tried to follow their disclaimer and read the notes but I cannot see if this is actually needed to upgrade...or why it is even listed as a step.
Also, are there any issues that could arise from converting the tables to utf8mb4 from utf8 and just skipping converting the columns to a different type?