SPNs placed on the service account objecdt vs place on the computers object

Hello,

I have read several KBs and articles on setting up SQL server with AD service accounts (from a security perspective) and setting up SPNs so I am looking for someone with hands on experience to help me get something.

I used the servers credentials to create my SQL instance and was able to connect via SMSS.

Then I uninstalled SQL and used AD credentials to install SQL.
Then using domain credentials I deleted the SPNs created with with "SPN -S MSSQLsrv\myserverName:1000 domain\UserAccountName"
Now the only way to get SMSS to work is using the IP of the server and SQL appears to be using NTLM authentication.

So why is the SPN created under the user ID?
Does this change the way and the credentials I use to connect to SQL?
Is the installation procedure I used wrong?