Are Congressmen(And Women) as civilians, accountable to the Logan Act?

You're really reaching. According to The Constitution the Legislative Branch declares war, NOT the executive. Now this has been interpreted many ways, and the reality has altered over the years (it says declaring war, not day to day military operations)..which is why we haven't had a DECLARED war since 1939....BUT.....the Legislative Branch ultimately also has control of the purse strings to the military and Budget. This means that there IS constitutional oversight of the military and President by civilians. It's called balance of power...so that one person can't do too much damage (I guess when one party controls the Executive and Legislative..and the media and opposing party don't have the guts to question decisions....balance of power breaks down and you end up with what we have now...a President and Republican Administration that have done DECADES of damage to our budget, world wide credibility, military, and regional balance of power in the Mid-East).