Safari Preferences Not As Prescribed

I asked my credit union for support because the bill pay portion of their site won't open in the intended tab, but instead it tells me I must enable 3rd party cookies or click a link to open the bill pay service in a new tab. Choosing to open in a new tab works, but I wanted to know how to change the settings to use the same tab. In my Safari 11 on Mac OS X 10.13.6 I do allow cookies and temporarily also allow pop-ups, and disabled my ad blocker.

The bank wrote me back with this message: "When I click on SAFARI I scroll down and click on Preferences. I then click on SECURITY and on my MAC it states Web Content and the options below that is Enable Java Script and that box is checked and below that is Block Pop-up windows and that is not checked and Allow WebGl that is checked. I also have Allow Plug-ins checked. Then I click on PRIVACY and where it states Cookies and web site data I have Always allow checked and where it states Web site use of location and services I have Deny without prompting checked."

Curious is that my privacy tab only has one checkbox for cookies "block all cookies" which is not selected, but my options don't include "always allow" as the bank employee wrote, and my privacy tab has nothing about location services. My security tab does have an option to block pop-ups, but I have nothing about WebGL and nothing about plugins. Curious. So I looked online and found Safari for macOS Sierra: If a website has WebGL graphics in Safari. But my preferences window doesn't have Enable WebGL under Security. I read elsewhere that I need to go to Advanced and Enable the Develop menu which I've done, and it's written that I should see Enable WebGL under Develop but in my menu it's not there.

I then saw How can I allow WebGL? which said WebGL is simply not there. Why the contradiction where the discussion doesn't match the support KB?

And why do my Safari preferences not have the same options as Safari on my bank rep's computer?

Is this because I have a 2011 iMac and need a newer iMac? It's running the latest OS X but I've found some thing like Air Drop are limited on this year.