So the Get-Service command lacks the property of the startmode so you have to resort to WMI to see that.
However the stupid thing is that the Set-Service command does allow you to do this and will handle piped in object names.
You’re basically executing in the blind. The best thing I can recommend is use your Get-Content with your text file and pipe that to the Set-Service command and use the -Verbose switch it will display confirmations in yellow I believe.
Get-Content E:\Powershellscripts\DisableTheseServices.txt | Set-Service -StartupType Disabled -Verbose
-VERN