Myth
Congress will control the convention process. Congress will select the delegates and set the rules for the convention including how votes will be cast. The source of this authority is the Necessary and Proper clause in Article I and in the power to "call" the convention is Article V.
Fact
Congress has the authority to "call" the convention. That power is limited to setting the time, place and purpose (Sec 3.9.2). The power to call the convention does not extend to anything else (like saying who can go and how voting works). Congress is not authorized by the Necessary and Proper clause to control any aspect of the convention.
How do we know?
We know from common sense. We know from the ratification debates. We know from case law. And we even have Congress itself rejecting, on multiple occassions, the notion that it can control this process
Just using common sense, we know that the founders didn't authorize Congress to control the convention. Remember why the convention was put into Article V in the first place : To give the people a way of amending their Constitution should Congress fail to act.
George Mason, during the Constitutional Convention, even observed that...
...no amendments of the proper kind would ever be obtained by the people, if the Government should become oppressive...
unless the states had the authority to propose and ratify amendments without the need of Congress.
source: https://avalon.law.yale.edu/18th_century/debates_915.asp
And these people who wrote Article V also wrote Article I. So you would have to assume a fair amount of stupidity on the part of the founders to think that they would grant to Congress in Article I the power to interfere in a process designed to circumvent them in Article V.
From the ratification debates...
We also know from comments made during the ratification debates that it's the states who control the process from beginnging to end, not Congress.
From the debates in PA...
"That the proposed Federal Constitution cannot be very dangerous while the legislature[s] of the different states possess the power of calling a convention, appointing the delegates and instructing them in the articles they wish altered or abolished."
From case law (Idaho v Freeman, Dyer v Blair)
The fight over the ERA in the 70's and 80's produced judicial opinions that undercut any claims Congress may make to exert additional control over the process.
In the Dyer case, the courts held that when a legislature or convention exercises a federal function, statutory law on the subject is advisory only. (For an explanation of what a "federal function" is, see Section I. Federal Functions)
And in the Idaho v Freeman case, here's what the courts said about Congress's authority in the amendment process...
First, it must be recognized that Congress' power to participate in the amendment process stems solely from article V…
Congress, outside of the authority granted by article V, has no power to act with regard to an amendment, i.e., it does not retain any of its traditional authority vested in it by article I
source: https://www.leagle.com/decision/19811636529fsupp110711473
Congress doesn't even think it has this authority
Over the course of our nation's history, Congress has proposed over 40 bills that would exert some kind of control over the convention process.
All of these bills failed.
So not even Congress believes it has the authority to interfere in the convention process.
Anyone who thinks that failed bills creates a legislative precedent needs to go back to law school
- Michael Farris, Chief Counsel Alliance Defending Freedom
source: