I have a 2018 Q70 with 18" wheels. Can I upgrade to the 20" Wheels and tires without changing brakes or anything else? TIA!

I dont see why not.

I did that on my 2015 Q70 earlier this year. If you stick with 245/40R20 tires, the speedometer will be correct, too. If I remember it requires 9" wide rims.

You could do 22's if you wanted but it would be a stiff ride.

If you go to discount tires they can look up your car and be able to give you size, width and offset that will work on the car.

I have the factory sport wheels which are
20x9 et43. These wheels clear the factory big brakes.

I also put 25mm spacers and they poke out a little bit but it's more aggressive looking.

Good luck

There are so many options that you can do.

Andy