It's actually a myth (or an urban legend) that the Windsor knots were invented by royalty.
Said Royal did prefer a larger knot, but achieved this look by using expensive custom made ties with thicker material or more layers.
The knot was invented by people who wanted the appearance of the larger knot without the expense of a custom-made tie.
That said, in summer I have been known to deliberately wear a tie made from thinner material for comfort, and then use a larger knot to bring the appearance back to neutral. However I'd tend to use a Pratt, Nicky or Albert knot than either Windsor variant.
You should also pay attention to the styling of your shirt, especially the cut of the collar, as the framing of the knot alters the perceptual appearance of the knot itself.
Likewise, the same tie and knot on a larger gentleman will look different.
There is no "one true knot" for all occasions, and as with any sartorial choice ones tie knot should be considered as part of the overall ensemble.
That said, the four-in-hand should be considered the default knot when one has no pressing reason to use any other.