Project layout size for laptops

I use the following web tool to see how much room I have on-screen for different devices and browsers.

https://howbigismybrowser.com 

Keep in mind this doesn't mean you have to use all the resolution of the browser viewport, but this gives you an idea of what the maximum viewport is for different devices.

First of all: it is the browser resolutuion which is important for HTML output.  Laptops can have many different screen resolutions as well, from rather low to 4K or even more. For choosing a resolution you also have to take into account in which 'evironment' the output will be shown: each browser and LMS needs also px from your resolution. Moreover you also need to know the bandwidth.

To have the output adapt to the learner's system, you can choose to publish Scalable HTML or create responsive projects.

Not the one size answer you expected. Have a look at the default sizes which you find in Captivate. The width/height ratio is pretty important. Most laptops have now a 16:9 ratio, but some still come in other ratio like 16:10.