Handlebar width, as any other part of bike ergonomics, is tied to your body size. Even people with the same body height can have different experiences with identical bikes, since human bodies vary in more than just height. Your shoulder width correlates most to the way your handlebars feel for example. While it is correct that wider bars can give you more stability due to leverage, if your shoulders are too narrow or arms too short this might put excessive strain on your arms while riding. This additional strain will lead to you not being able to use proper strength while controlling your bike, thus less stability overall.

Before cutting down your bars, you should always try and get used to the new ones first. Humans are animals of habit after all and sometimes it takes a bit of time to break old habits. If you still have your old bike avilable, you could also try and switch bars between bikes for comparison. If, after all that, you still decide to cut down, you might want to take smaller steps. Maybe cut down to 790 first and see how that feels. You don't want to cut off too much right away. While it's easy to cut stuff away, you would need new handlebars in case you find 780 too short on your new bike.