I did all 4 the same, I thought since that’s the way the 19s are delivered from the factory, I would be safe and stay that way although with the 20s, I can easily move up one size of tire for width. Remember, with offset, the lower the number the further the physical wheel is away from the internal parts of the car, brake caliper and such higher in sets, move the wheel closer and closer to the brake mechanism, I’d rather air one or 2 mm wide, and away from the brakes than the other direction.