I like messing around with different strings because it’s fun, but otherwise it really isnt important. I set up the light and floaty Doc Pop Icarus with some nylon and it feels like im playing on clouds. It is just another aspect of the hobby to enjoy.
As for pros, they are typically more focused on nailing their tricks as consistently as possible, and since different strings react in slightly different ways, it would probably be to their detriment to experiment around with it too much. I don’t take what pros do for gospel though, since I play for different reasons. They can use Kitty if they like. It’s a nice string, but I prefer something like a Zipline (perfect length, I dont even have to think about it) or Plutonium since they feel better longer and last longer. Personally I get satisfaction out of trying different strings on the same yoyo and seeing how they feel.