Your Base64 encoded private key is the "raw entropy", an uncompressed WIF private key tells the wallet to derive an uncompressed public key from the private key giving you an uncompressed public address.

From the same Base64 encoded private key you can also get a compressed WIF private key (fun fact: it's one byte longer than the uncompressed WIF; the compression property is not refering to the size of the private key), which tells a wallet to derive a compressed public key (which is significantly smaller than the uncompressed public key) and finally a compressed public address.

It actually doesn't hurt if you import both the uncompressed and the compressed WIFs into your wallet. That way you don't miss any UTXOs.

As highlighted by others, it is essential that you operate in a secure and preferably offline environment which can be easily disposed completely so that it doesn't leave any data traces behind. A live Linux that you can boot from an USB stick is quite handy in that situation. As it usually only runs in RAM, everything is gone when you shutdown. Make sure to save your wallet or any other valuable data before you shutdown, but keep exposed private keys always offline.

Private keys should be stored in encrypted wallet files, not as exposed unencrypted private keys on storage media. If you accidently attach such a storage media to an online device, you risk to compromise exposed unencrypted private keys.

Play it safe. If in doubt, learn first or ask first.