Nothing to see here (aside from the fact that that really IS the inside of a Lockheed Neptune ASW aircraft, that really IS the wing that runs through the middle of it, and you really DO have to climb over that and through that narrow gap to get from the front to the back.)
But this is about LightRoom, and is just helping out a fellow P-Baser with publishing (export) settings.
Rather than exporting in inches (which have no meaning for screen displays; they relate to printing only) it's better to set the longest size in Pixels. This will ensure that it is sized (relatively) consistently on all monitors.
Anything over 72dpi (strictly speaking it's PPI for screen; pixels per inch but we'll use Dots per Inch for convenience) is wasted on a screen display. As most of them are either 72 or 96dpi (for now at least) the 300 DPI used for printing just means content density that isn't used. (Larger files for no benefit.)
The pixel size chosen should reflect the approximate size of the viewer's screen so that they can look at it and see most if not all of the image when Original size is selected. PBase still uses 800 pixels on the long edge as its "Large" display even though that's a throwback to the days of yore. These days 24% of my visitors have a screen size of 1366*768, 23% have 1680*1050 and 22.1% have 1920*1080. Though about 10% still have between 1024 and 1440 pixels wide, not counting the 17% or so viewing on mobile devices.
So I figure that about 1000 or 1200 pixels wide is the sweet spot at the moment. Not too large to fit on a screen, not large enough to be worth stealing for a printed copy (it happens, people don't just want but believe they are entitled to something for nothing these days), and not so small that details are unnecessarily lost.
For portrait shots I still stick to PBase's "Large" size of 800 pixels high because I still have a full quarter of visitors who can't see a full sized portrat image when they select Original size.