The big mystery is the Virginia Grand Jury. Would they have any role in evaluating potential federal crimes? Crimes that fall under potential presidential pardon power?
If not, there must be smaller fish Virginia residents across the Potomac in Mueller's crosshairs who would face state crimes, immune from Trump's pardon power.
Also, if a Papadoplous type is pardoned, and Republican congress turns another blind eye re impeachment, is said pardoned person subject to subpoena before Congress, and has no fifth amendment right to assert, but faces new crime if perjury if later found to have lied to congress? Hence another pardon? And of course another blind eye by Congress re impeachment.