USB Serial Drivers and CHIRP software

First, the bad news: I am not familiar with CHIRP or the Baofeng radio, but from what you describe I think you're on the right track.

The Prolific driver is one of two common USB to serial devices used on macOS and the fact it appears in System Profile indicates it's doing everything you can expect it to do. That leads me to believe the roadblock preventing communication lies in the CHIRP software and / or the radio or any connection cables involved.

In circumstances such as yours I reduce complexity as much as practicable, and toward that end I suggest downloading a simple serial communications app such as SerialTools. It's on the Mac App Store and it's free. Use it to determine if there is any activity whatsoever at the serial port. The app itself isn't very robust but its user interface is simple, and altering things like communication parameters is easy. A serial breakout box with LEDs or something like it might also be worth the investment.

For what it's worth I use Keyspan (now Tripp-Lite) USB to serial converters, in addition to other commonly available Prolific chipset devices. They work without complaint.

If and when you decide a more robust serial communications app is required, I recommend the rather unfortunately named Serial from Decisive Tactics. Phenomenal app that continues to work with Big Sur and M1 Macs. Not free but worth every cent. The Serial app incorporates drivers for most serial devices including Prolific, so there will be no need to concern yourself with that any more.

I downloaded the SerialTools app but could not see any activity when I tried to connect using CHIRP. I downloaded the trial version of Serial and though it opened the port, from that point on I was looking at an empty terminal window and had no idea what to do.

You type. The characters you type magically appear in that window if the device at the other end is set to echo characters.

Since that's not happening, perform your own loopback test (connect Tx and Rx) and don't bother doing anything else until Serial shows what you're typing.

Once that task is successfully accomplished, macOS itself and your Prolific device are doing everything they can do. That isolates all remaining problems to CHIRP and everything connected to the USB to serial converter.

Serial acts like a dumb terminal. It sends and receives; that's it. If you connect Tx to Rx and type characters, do they appear in its window?

I downloaded and installed CHIRP. It runs, but without a radio I can't do anything with it.