There is a balance to be struck, for sure. However I think we're currently out of balance and have been for many years.
This is in the context of declaring war but it also applies to appropriations, executive orders & executive privilege.
IMO, the out of balance part is due to Congress delegating too much power to bureaucratic agencies and writing vague laws that the executive branch gets to interpret. Executive orders come out of the second part. Also, I was thinking Presidents have always chosen not to enforce certain laws or enforce other more than anyone expected. Congress can change those laws.
I am not sure I agree on the executive privilege part. I don't necessarily think the majority party in Congress should be able to drag anyone they want into Congress to testify especially when they are doing some sort of fake impeachment investigation. They are just playing politics and I think the President should have some leeway there.
The Federal Govt shouldn't be so big and intrusive that we can't wait for the next election to decide things.