The chrome inspect tool is the only one that can give and idea as to how your website will display. That is why now and then I go to an apple store, specially with the new screens that the X's have the screen does not fit well. I have also used https://www.browserstack.com and they are expensive, plus they do not carry the latest iphones. So yes, if you can get yourself an apple phone, and ipad and an andriod then you can test them out but anywhere else on the internet you will not get the auto fit screen effect from a software. I believe it is hardware that fits the screen within the viewing area. @Rob can chime in on this, their team is looking into break points and why the new phones have issue with this.