I am pretty sure I saw this on one of TTG’s You Tube videos but can’t find it again.
When wanting to see how a page is displayed on various screen widths including iPhone, iPad etc etc there appears to be a page or maybe a browser plugin to select a virtual screen size.
So you can see how a gallery or album will display on iPhone for example without getting your iPhone - if you have on - out.
You shouldn’t need a special plugin or installation. I think all browsers have the Inspector tool built in. Firefox, Chrome, Brave, Edge, and Opera all have it.
I don’t know about Safari, but I imagine it has developer tools as well.
This is from the Firefox Inspector. In the upper right is the Responsive Design Mode button
In Safari, you have to go into the settings to enable Developer options. In Chromium based browsers, you should only need to open the dev console to find the responsive design features.
That’s what you’re looking for, btw: Responsive Design features.
You would only need Xcode and its simulators if you were developing an app, which you are not. Extremely overkill for what you need. You should be able to do all you need to do within the browser, either by resizing the browser window to whatever size, or by using the responsive design tools now present in every major browser.