Don't forget, Schniederman is still preparing state RICO charges concurrent to the Mueller investigation. Any of the criminal acts that took place in NY (Trump tower) will be subject to NY charges which the president cannot Pardon. Mueller and Schiederman have been cooperating on the investigations and sharing information.
Manafort is first, because his charges are kind of a layup. Any plea-deal will almost certainly involve a felony elocution so that a baseline criminal act for obstruction charges against others. My understanding is that an underlying criminal act may not be required for obstruction to proceed, but it would be better if such an act were established in the record.
As to impeachment, Trump's racist outreach program over the last few months has been a strategic display to energize his base to primary challenge any potential R impeachment votes up for reelection. The entire White House culture war strategy of the fall has been about trying to impeachment-proof congress in the mid terms. If they succeed and impeachment has been grounded by a wingnut wave election overturning the establishment GOP
We may end up seeing in lieu of impeachment is a VA federal grand jury and NY State Grand Juries issuing true bills against a sitting president. It will then likely be up to the supreme court to determine if such a true bill can compel a criminal trial of the president rather than impeachment. Both Star (Clinton) and Jaworski(Nixon) prepared legal arguments in favor of indicting a sitting president as contingency for congress failing to impeach. It is not settled law, but convention.
Unfortunately, I have zero point zero percent confidence that this Supreme Court (with Gorsuch as swing vote) would uphold the indictments. But, the fallout of of the congress and supreme court protecting a president from and already handed down grand jury indictment might be too much stress for the system to take.
If I had to wager, I'd bet the outcome will be admission of Trump's dementia(no guilt) and 25th amendment removal for the sake of the republican party before anyone has to go on record against impeachment or god forbid stonewalling grand jury indictments.