Weight won't change your playing style at all.
Some of best players were skinny .
Bird, mchale, KG, KD, AD.... you name it.
Kukoć entered pro career being 6'11 -185 . They called him pink panter because of skinny legs.
In same time in league you still have legit 7 footers who bang down low ( Nurkić , Jokić)
but you also have some "bullyball" players like J. Randle who is 6'9- 235 pounds.
In general if you track average size and weight, nba players did gained some weight at average until 2013, but new thrend is trimming down.
Isaac ,Bamba or whoever won't become better player by adding more weight. That's why that " prime is around 28" is myth at this point. Most players by the age of 28 actually decline and part of them peak later. There is no set "timetable of greatness" for any of them. It's just honeymoon rookie contract relation between fans and player and " legit expetations based on new, big contractt" .
Some of biggest nba stars today are all in their 30s ( Durant, Curry, Westbrook, Lebron). Lebron and Curry are 35 and 32.
Lamarcus Aldrige is comming off his best season in career, guy is 34
on other side Ibaka , Love , Bynum, Howard, Arenas, T mac , Deng... all peaked early and flamed out
"A straight path never leads anywhere except to the objective."