It's like talking to a brick wall...
I'll try dumb this down for you.
Yes he was fighting differently which ultimately makes his fighting style different which ultimately makes his fighting capabilities less his strategy in the fight was to get Law's heart back and in order to do so he had to get close to Vergo which meant he had to take hits from the Haki beast which again weakened him.
Yes Smoker more than likely knew Law could beat Vergo with his devil fruit power.
Had Smoker used his 'usual' strategy I believe he would have been able to push Vergo to the point Vergo would have to use full body CoA and again this isn't a baseless statement the fact Smoker was using a strategy that was very unlike his usual one made him weaker which again I feel the need to stress this meant had Smoker used his usual strategy he would have been able to put up a stronger performance.
