The design intent of the game is to make players play like themselves, in a balanced game play experience, at SS sim and AS sim. The difference between the two is SS sim gets a bit more of the CPU artificial intelligence and adaptation.
So, for example, on defense, the CPU will be more aware and react to your offensive action more quickly. As a result, your shot or play making windows will be narrower and so you will have less time to read what's happening and make decisions. Your margin for error is less. This is not accomplished with ratings or attribute boosts but with more complete and quicker acting offensive and defensive AI.
Using default sliders will make the game a little more arcade like, and less sim. Using All Star or Super Star sim settings should give you what you are after. That said, just because the designers targeted and tested the game to be most sim and realistic on those settings, it doesn't mean they got it all perfect out of the box. You or others in the community may find that making a slider tweak here or there improves the game.
I've done custom sliders for years, and this is the first year where I am really taking my time to play and understand the game tuning out of the box before concluding I need to do much with sliders. I may go there, but they did a much better job this year than in previous years in approximating real sim game play on AS sim and SS sim.
So, depending on your skill level, I would start with one of those and play enough games to get a good sample, against enough teams (who really do play differently this year). Then, once you have a feel for how your chosen level fits with your skill level, start checking out the slider sub forums for ideas on any tweaks you may want to try.