Actually the drag on the pedals is the same for 4 stroke or 2 stroke, all other things being equal.
You can pull and lock the clutch on the 2 stroke so there is no engine drag, just like the centrifugal clutch on the 4 stroke.
You will still feel the chain and tensioner drag on either.
On the other hand, the extra 10 pounds (approx) of a 4 stroke is another 10 pounds to get up a hill.
The tensioner will have very little drag if designed properly. Installed on the slack side with a slight bit of slack and minimum deflection angle with light (preferably 410 or BMX type chain) and well aligned will have only a slight friction. Spring loaded tensioners will have more drag and friction. Even better, remove the chain for a long ride without the motor. It only takes a screwdriver.