I read it as saying the VP AND the majority of either the executive branch principals or the congressionally created group must sign.I don’t think Pence would sign.
The 25th amendment says "Whenever the Vice President and a majority of either the principal officers of the executive departments or of such other body as Congress may by law provide...
That means that Congress has to pass a bill that creates this "body," and then that bill must be signed by the President to become law. If the President vetoes the bill, then Congress can override the veto to make it law.
Once it becomes law, then that "body" can support the Vice-President in removing an incapacitated President under the 25th amendment.
-PJ