The antifreeze looks dirty. I would not go so far as to say it has oil in it. However, if the system was not flushed before putting in new antifreeze, you can get a mixture of the dirty and new especially since the bike sat for 7 years antifreeze can get dirty sitting in a radiator that long stagnant.
As far as the plugs, if they are getting dirty/wet, you have to determine what they are wet with (oil, gas or antifreeze). If the head gasket is blown, there is high likelihood that the plugs on that side would be steam cleaned. If it is oil, it could also be a blown head gasket. If it is only one plug and smell anything like gas, it is still a carb leak.
I do not want to assume anything, but need clarification. Your compression readings indicate the left side (2&4) are nice and tight and the right side (1&3) are lower, but not too bad for a bike sitting 7 years. I want to be sure we are on the same page; left side (2&4) is left as you sit on the bike right? (Not left looking at the engine from the front tire looking back?) I only ask because it has happened before that folks understood left and right looking at the engine.
Either way, does the white smoke show up as soon as you start the bike or only after the engine is fully warmed up? FYI, antifreeze burning off out the pipe still smells like antifreeze. Gas creating a white cloud is not always easy to tell, but, with #4 being wet, I am still leaning towards the #4 carb is pouring gas into the engine. I have had this happen before!
Just trying to rule out everything before you pull the heads.