I'm sure that many in Congress and government in general would agree (unless it is something they don't want to do). "Unless it is an explicit and specific restriction, there are no restrictions on the power of government!"
That is not the position I'm taking as a general rule. But when it comes to powers that are explicitly given to Congress, in order for them to be restricted to something more limited than the words used, interpreted in accordance with the context, such as would be the case if impeachment were to be restricted only to current office holders, excluding those no longer in office, then that restriction would need to be explicit, or at least implied. But such a restriction of impeachment is not even implied anywhere in the Constitution. Meanwhile, the power to give a sentence that applies to former office holders, and not only current ones, is explicitly given to the Senate in its trying of impeachment cases.
All of the powers that are enumerated in the Constitution include within them all sorts of things that aren't explicitly mentioned, and don't need to be, inasmuch as they are necessary and proper to the exercise of the power that is enumerated.
Granted, even at that, there are bound to be debates about what the enumerated powers do include. And the debate we're having may be an example of one.
In this case, both your position and mine could be seen as the one that restricts government power more, depending on which side you're looking at it from. My position is the one that exposes government officials to the greater degree of accountability for misuse of their power. I sincerely wish more presidents and other office holders would get impeached as a fairly regular thing for a much wider range of offenses than most people think impeachment should be limited to, and believe that if they were it would give them incentive to be less brazen.
Does the Constitution explicitly say that the Congress can not over-turn electoral college votes from the States if they believe that it is important, necessary and something illegal happened?
The 12th Amendment explicitly says something equivalent to that.
That said, the Constitution does give Congress limited power to pass laws that regulate how states choose their electors in the provision that it must guarantee that the states have a Republican form of government, and in relation to the specific demands made in the 14th, 15th, and 19th Amendments. If the Trump allies were serious about the show they put on January 6th, they should use the power the Constitution actually does give them, rather than a power it doesn't, and introduce legislation that would preempt the kinds of illegal selections of electors they're worried about via federal law that includes provisions for dealing with states that try those things. Maybe some have and it hasn't gotten any coverage, I don't know.