I have the following query to get me a list of sysadmins in the current server:

select 'ServerRole' = SUSER_NAME(rm.role_principal_id), 
       'MemberName' = lgn.name ,
       'Status'= Case when lgn.is_disabled=0 then 'Enabled' 
                                             else 'Disabled' 
from sys.server_role_members rm 
INNER JOIN  sys.server_principals lgn 
        ON rm.member_principal_id = lgn.principal_id 
where rm.role_principal_id = SUSER_ID('sysadmin') 

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Should it be a concern that the accounts starting with NT SERVICE are sysadmin?

the sql server agent service is running under the account shown above in the item number 10, so maybe the number 7 is even redundant, how can I find it out?

There is a similar question:

Is it viable to attribute permissions to SQL Server virtual accounts (NT Service\SQLSERVERAgent, etc)?