SEPM Database migration

Hello, 

I checked some articles regarding DB migration from one server to another but I did not find answer for my three question. Article which we will use during migration is https://support.symantec.com/en_US/article.TECH132761.html

My two questions are:

1) What is "sem5" user ?? Every SEPM use this user or we can have different user which is used for DB connection? 

2) Why "sem5" user need to be deleted? Can we just move users as well? 

3) Management Server Configuration Wizard  - it is this wizzard which I can find in menu start in SEPM tools?

Thanks in advance.