How to load certificates (PEM, SPC, PVK, NET)?

The FTP/SSH certificate page states being able to load the following certificates.

• PKCS #12 (.p7b) and PFX (.pfx) files. These usually contain a private key.
• DER files (.der/.cer), either binary or Base64-encoded. Private key can be loaded from an external key file

The examples are great, yet I am missing some details on how to load other certificate types. These are;

• PEM - used by OpenSSL package (Is this just DER with key?)
• SPC, PKCS#7
• PVK
• NET (PKCS#8)

I must admit that I don't fully understand all of them, and sadly don't have the time to invest. Our previous library supported these, and therefore they were exposed to the user has part of our feature set.

So my question is, how do I load each of these certificates? Currently I only see LoadDer and LoadPfx methods.

Thanks.