I wanted to know if anyone has an answer for me. If i still have my public/private key, can i withdraw the BTC that i previously put into PlusToken using those methods since Plustoken has shut down?
No, they are known to be one of the biggest scams in history. Even if you have your private key, you cannot simply withdraw it and get your money back. They are scammers, they already have taken your money and there is no way to bring it back. As you have said, Plustoken has shutdown, meaning there will be no one in here who can answer you on how to bring it back but the team itself.