Does Congress have any "enforcement" capabilities?

Is there anyone who can be sent to the offices of the RNC (or wherever) to seize the servers and recover the "missing" emails? Does Congress have any arms and legs?

Seems to me like they should have. . . .

Because of the separation of powers, Congress can only make law; it is the Executive Branch's job to enforce the law. If the Executive refuses to enforce the law, or if (as definitely seems the situation here) the Executive is actually breaking the law, it is the Court's job to implement such penalties as are deemed appropriate. But with the way the White House has been stacking the federal courts, it is very unlikely that the Supreme Accomplices will do squat.

no way to see to the safety of the evidence?

Under a strict interpretation of the Constitution, only the Executive Branch has the power to seize and protect evidence. It is possible based on US judicial precedent for the Judiciary to deputize others to perform that job, except that A) the federal judiciary has been packed by the criminals under investigation and B) it would be trivially easy (and technically correct) to say that such a deputization violates the principle of the separation of constitutional powers in that the Court is assuming the power to execute the law.

The Constitution assumes that only one branch of government would be corrupt at a time, and balancing the actions of one corrupt branch requires the cooperation of the other two branches. When two or all three are corrupt, there is very little that can be done short of a second revolution. From the late 20th century, the fears of the Federalist Party have been realized in full: the people can not be trusted to be the final check on government.

I believe that Congress can use it subpoena power to examine the information on the RNC servers, if it is tied to their investigation of wrongdoing. Can anyone verify that supposition?

The power of Congress to hold investigations and hearings is strongly tied to their authority to pass laws and pursue impeachment. Arguably, it would be unconstitutional for Congress to turn over evidence collected as part of Congressional hearings to the courts for prosecution, as that makes Congress an adjunct of the Judiciary and thus violates the separation of powers (ie Congress is not allowed to do the courts' job.) If Congress investigates and decides that wrongdoing has occured, the Constitution allows only them to: A) draft legislation which would have to be signed by the criminals under investigation in order to become law, or B) begin impeachment proceedings against the people responsible. That is it.

different rules apply. They can ask, but the RNC could ignore congress or plead the fifth.

How can we keep the Administrative branch from destroying evidence??

But honestly: what are the chances of that?