Borg might have been the only player who used topspin both on the forehand and backhand side consistently well. And it was said that you couldn't win too many Wimbledon by staying back or from the baseline, but Borg clearly overrode that when he went on to win 5 of them. But that's also perhaps why Sampras wanted to change his play style from the baseline to S&V, since he really wanted to win as Wimbledon as possible and he did that too. Federer came afterwards and not before Sampras so he was more looking at what Borg had done than what was going to happen in the future, since he had no way of knowing it.
Now thinking back, had Sampras continued with his baseline game, then perhaps he would have not won as many Wimbledon or perhaps equaled Borg and perhaps, he could have won a couple of FOs. Because rest assured, clay surface definitely requires a baseline game due to its super slowness. That might have been the reason why Federer stuck to baseline as well though it still did not give him more than 1 RG.
It's amazing that Borg was able to win 6 RG and 5 Wimbledon and 3 times both in the same years. And his demeanor was cool as cucumber while under pressure, something that Sampras was also very famous for. Federer used to lose his temper a great deal initially, but after he started winning but perhaps more importantly, when he realized that his temper wasn't really taking him anywhere, he cooled off a lot. Nadal is also not known for losing his focus or temper even when under a lot of pressure. I really think it's more natural than contrived unlike Federer's.