Am I able to use a BIP32 Extended Master Private Key (xprv) to import an address or address’ to Counterwallet?
Or, will it require that I derive the individual Private Keys (WIF)?
If you have your passphrase, you can just login with that otherwise you import individual private keys.
I don’t know but just try it. If it accepts the first private key format then you see your tokens and can import and sweep. If not you need to use the second private key format.
FYI if you input a private key in counterwallet, you will be “sweeping” all of your BTC and other assets into your counterwallet address. If this is not the desired behavior, you probably don’t want to import your private key to counterwallet.
You might want to check out freewallet desktop or freewallet mobile at freewallet.io. Both wallets allow you to import a private key and use the associated address. This way your able to USE the address rather than just move everything out of the address (aka Sweep)