Modifying schema

I was curious if people here modify the default schema? Examples I am talking about are a. adding additional indexes, b. changing TINYTEXT to VARCHAR(255), Changing VARCHAR columns with data types like ‘yes’, ‘no’ to ENUM(‘yes’,’no’)

Also change MyISAM to InnoDB.

I am looking at a high traffic site and am examining ways to optimize an existing schema which will be ported to a new system and redesigned etc …