Launch Configurations and Launch Templates perform the same task. They provide the WHAT to Auto scaling groups. They define WHAT gets provisioned.
The AMI, the Instance Type, the networking & security, the key pair to use, the userdata to inject and IAM Role to attach.
Launch configurations have one use: they are used for Auto Scaling Groups.
If you need to adjust the configuration, you need to create a new one and use that new configuration.
In addition to Launch Configurations, they can also launch EC2 instances from the console/CLI.