I own a '16 Impreza and it really drags at low speeds. It's my only complaint with the car however, and it is better with higher octane fuel.
Unless you're getting premature ignition in your cylinders from compression (knock) the higher octane shouldn't matter.
If its a turbo (i assume not?) the car’s ECU will compensate for lower octane. Source: me when, half asleep, I accidentally half-filled my 03 WRX tank with 87.