Azure Sign Tool is an implementation of Microsoft’s SignTool backed by Azure Key Vault instead of a certificate in a certificate store. This is used by Sign Service.
Open OPC Sign Tool allow signing Microsoft VSIX packages with a certificate in the certificate store, on file, or using Azure Key Vault. This is used by Sign Service.
Fiddler Cert Inspector is an extension for Fiddler allowing inspection of the certificate chain presented by the server. This is useful when you want to view the certificates in an HTTPS connection while Fiddler is performing HTTPS interception. When Fiddler performs HTTPS interception, the browser shows Fiddler’s generated certificate - not the one sent by the server.