Hi, Tom
Clicking while coasting is normal. Some gears are louder than others.
Oil from drain plug not normal. Perhaps it is just not tightened enough and just needs a tweak. "Do not over tighten, though", The screw should stick out from the hub shell a bit. The absolute maximum is having the top of the screw level with the hub shell. Mine is never that tight and never leaks.
Oil on cog side is normal. Some leak more than others. It should also diminish when the bike gets ridden and the cog gets really tightened up.
All the best
Ron