I will pose a few example to make sure I understand your question correctly.
“Will Chrome on Linux ever be below 400px wide?”
“Will Safari on MacOS ever be below 800px wide?”
“Will IE on Windows ever be above 1400px wide?”
You should not be worrying about which browser your site is being viewed on. Most browsers can be resized to below 320px wide. There are no standard browser window sizes because a user can resize them as they please.
I would personal use media queries to detect when the browser window is below or above a certain size, thus removing the need to worrying about which browser a user is running.
I hope this answers your question in someway.