Check out the rest of the videos in this special course: The Practical Guide To Mac Security.
While private browser windows are a good privacy feature, they don't protect you from malware, account break-ins, or other security issues.
Check out The Practical Guide To Mac Security: Part 18, Private Browsing at YouTube for closed captioning and more options.
Regarding Safari's "Privacy Browsing", I have a separate computer (Google Chromebook) for doing all my visits to financial asset websites because I am trying to lower the risk of someone hacking and obtaining my personal data. However, if that computer is termporarily down, what protections, if any, would I have logging into my iMac (Safari browser) using the Privacy browsing mode versus the regular browsing mode?
Gary: None. That's not what Private Browsing is for. You want security, not privacy. Privacy would be like if you went to a site for airline tickets and then that site shared that information with other companies and you started getting ads for vacations. It has nothing to do with security like what you need when you log into a bank site.
If you are using your iMac in your home, just log into your bank as normal. No need for a Private window or anything like that. Using a different computer doesn't help. It may hurt in that you now have two computers you need to keep free of malware instead of one.