You can sign all other papers ( unless you have plan to sue Intel for wrong full termination) when taking VSP/ISP etc. Also, even if you sign their papers to take take VSP/ISP etc buy out, you still can sue for wrongful termination but Intel will use the RELEASE Form you signed as affirmative defense, but technically it will not stand.
However, YOU ARE NOT OBLIGATED TO ATTEND THAT STUPID LEGAL EXIT INTERVIEW OR ANY OTHER BULLSHIT HR INTERVIEW AND YOU CAN REFUSE TO SIGN their Trade Secret Acknowledgment form. Intel policy says that if an employee refuses they can only send you notice tell you could have been exposed to Intel IP. ALSO dont have to reveal, in case you have job in hand, whose will be your new employer.