fps Pixel 8 and 8a comes in 128GB and 256GB while the 8 Pro also has a 512GB and 1TB version. You can check the Google store page of your country to see what's available to you, e.g. the 1TB is out of stock where I am...
And the storage is not expandable, so make sure you choose enough space for as long as you use the phone which could be up to 7 years...