Are the certificate backup files encrypted with a private key?
If so, that would prevent inspecting them externally with something like a text viewer.
One thing you could do is write a PowerShell script to enumerate across the certificate files in a folder and restore each to a local or dev SQL Server instance and then run the following script to query details.
SELECT
@@SERVERNAME AS server_name
, c.name AS cert_name
, c.pvt_key_encryption_type_desc
, c.thumbprint
, c.subject
, d.name AS database_name
, d.is_encrypted
, dek.encryptor_type
FROM sys.certificates c
LEFT JOIN sys.dm_database_encryption_keys dek ON dek.encryptor_thumbprint = c.thumbprint
LEFT JOIN sys.databases d ON dek.database_id = d.database_id
ORDER BY cert_name, d.name;
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho