Mayweather has always adapted to the opponent/circumstance in front of him. While there were some changes in his style once he got to 147, it often gets exaggerated in terms of how offensive he used to be and how defensive he became. At 130, he had fights like Goyo Vargas, where he was very defensive, which came right after he fought Carlos Gerena, a fight in which he threw a lot of combinations. Sometimes people bring up the Corrales fight and the 5 KDs as an example of him being more aggressive and offensive-minded, but that was a case of him landing absolutely perfectly timed and placed punches on a fairly chinny guy. He fought a perfect fight, but it wasn't a case where he was throwing a lot of combos or being aggressive. He was mostly on the backfoot. He actually was more aggressive in the first 3-4 rounds against Carlos Hernandez in his next fight, where he was in the pocket more, throwing more combos. But then he hurt his hand so he went on his bicycle. At 135, he had two of his more dull, defensive performances (Castillo 2, Sosa) and also the two fights in which he arguably threw more combinations than any other fight (Augustus, Ndou). Just to add, I think the Sosa fight may have been the fight in which he most often used a jab to the head. More often, he used it to the body. He had the best jab to the body I have ever seen. At 140, he was pretty offensive minded against Corley, almost reckless at times, he mixed in offense and defense brilliantly against poor Gatti, and to a lesser extent, Bruseles. At 147 and up, while I agree there is a difference overall in his style overall, again I say that it's also a case of him adapting to the opponent and circumstance. He had some dull, defensive performances at the lower weights and had some aggressive performances here in addition to the more cautious ones. He spent much of the Judah and Mosley fights on the front foot walking them down, and this was after Mosley hurt him in the 2nd round more than anyone else has hurt him. He was fairly aggressive against Mitchell, Ortiz, and the first fight with Maidana. He threw more combos against Cotto at 154 than he had in a long, long time. The thing I did notice at 147 and above was that Floyd clinched more often. Against Hatton, it was seemingly by design to throw Hatton's rhythm off, then once Cortez let them fight, Floyd got the better of it in and out of the clinches anyway, constantly digging in that right hand to Hatton's body. But against Maidana, it was more of a defensive and stalling tactic. And he held seemingly whenever Oscar and Pacquiao got close. I thought it was a bit curious because I always saw Mayweather as a more refined, skilled, educated in-fighter than both Oscar and Pacquiao, who were better at mid range (long-range in Oscar's case). I was expecting him to fight on the inside and get the better of it there, so I was kind of disappointed in his performances in that regard when he just clinched.
The question that nags me whenever discussions like this come up is why more fighters don't adopt the Mayweather or Ward style; you are more than certain to win because you hit and don't get hit. Surely every boxer knows that taking unnecessary punishment is certain to result on serious health problems later. I am not sure Gatti or Alfedo Angulo would have fought/fight the way he did/do if they had/have a choice.