I've been 3D printing since January 2013 (mostly on a Printrbot, just recently upgraded to Prusa). In my experience, the settings in the slicer should not be regarded as "black box". Any "presets" are just starting points. The more you look at them, play with them, study the results, and so on the better you will be at improving the results on your particular printer with the particular filaments that you use and for the particular type of printing you typically want to do (i.e. large objects or small; toys and sculptures for games or decoration; mechanical parts for drones or models; upgrades to your printer, etc. etc.). I can't speak to how the presets were determined for the 2.5, but they were created by humans. I've downloaded slicer settings that were supposedly optimized for TPU filament, for example, and just looking at them I knew that there were a couple of parameters I needed to adjust before I even tried one print. That kind of knowledge comes from experience. Dive in, experiment, and have fun!