As you may know, BB no longer compresses data in OS 10 and BB Protect is not doing a complete backup anymore. The only serious camera is on the Passport. While the Note 4 has an enthusiastic following, is it open to malware?
The stylus helped this long-time keyboard user. It's hunt and peck, but it's better than a fat finger on a little keyboard. (SwiftKey Keyboard helps too.)
As far as malware, anything connected to the internet, from a remotely-accessible copy machine to a mainframe, is open to malware. If it can run software, someone can write software to make it misbehave. BB is no more immune to malware than Windows is. (It just has such a small user base that no one bothers writing malware for it.) Always run Malwarebytes Anti-Malware (if it's available for that computer) and a good antivirus app on any computer connected to the internet.