Can my 2019 subaru handle 322 horsepower if it's stock?

LOL! Not gonna happen. The chip might add a horse or two but not 170.

I suspect the chip maker is actually claiming you can get 170 hp total with their chip (highly doubtful). A chip may void your warranty and make your car not pass smog check.

Look, the Subie 2.0i is indeed an anemic motor, especially when trying to crank its CVT. The only upgrade path is to trade it in for the new 2.5i next year. A CAI, open exhaust, etc., just won't work. Many have tried.