You can use platform level device keys for Device type and OS, here is the doc : Device Targeting With Platform-level Keys
I cannot see any specific key for browser here. So you can use JS on a page to fetch the browser name and version and pass that in a signal (Key=Value pair) using pixel on that page.
If you want to create different traits based upon browser type (desktop/laptop browsers) then you can use following rules while creating rule based traits :
Trait Name : Browser Chrome
Rule: "h_User-Agent" contains "chrome/"
Trait Name : Browser Mozila Firefox
Rule: "h_User-Agent" contains "firefox/"
Trait Name : Browser IE
Rule: "h_User-Agent" contains ".net/"
Trait Name : Browser Safari
Rule: "h_User-Agent" contains "safari/" AND NOT "chrome/"
Similarly you will have to check User-Agent in demdex event calls and create traits for other browsers.