I haven't touched Madden 21 since Madden 22 came out.
Generally, the Senses Pressure trait affects the maximum radius at which a quarterback will "feel" pressure. Paranoid sets the radius to the maximum possible distance, while Oblivious sets the radius to the minimum possible distance.
My guess is that a CPU-controlled quarterback with the Paranoid senses pressure trait will probably rush throws before he would actually get hit by an incoming defender, possibly resulting in inaccurate passes, while a CPU QB with Oblivious will wait longer to throw the ball and risk hits, sacks, and sack-fumbles.