imac slow opening email, safari, etc.

Your computer shipped with Apple's Fusion drive. The report shows the small SSD, the remaining bit of Fusion hardware:

Drives:

disk0 - APPLE SSD SM0032L 28.00 GB (Solid State - TRIM: Yes)

Internal PCI-Express 8.0 GT/s x2 NVM Express

Replacing the mechanical portion of a Fusion Drive system with an SATA 6B SSD likely gave you slower speeds than Fusion. However yours are dismal. I have a Mac that I upgraded to SATA 6 SSD and it does 500mb/sec all day. A working Fusion system in your iMac model would do Writes of 500-900 MB/sec and read up to about 1400 MB/sec.

I agree that the BX drive was flakey but I noticed you did not enable TRIM on it:

disk1 - CT1000BX500SSD1 1.00 TB (Solid State - TRIM: No)

Internal SATA 6 Gigabit Serial ATA

Please do so, then do a safe boot. NOTE that you need to let the computer "soak" in Safe Mode for 30-minute to an hour to allow Safe Mode to finish its housekeeper. Without TRIm enabled, an SSD can run OK for a wjile— several years in my case— but then slows to a crawl. Write speeds fall first

Instructions you need are here:

Start up your Mac in safe mode - Apple Support

and here:

How to Execute ‘Trimforce’ Command with Your SSD

That does not cost any money, just an hour± of your time. If your SSD speeds remain abysmal afterwards, then consider a better drive.

I concur with WheelieNick

The CT1000BX500 SSD is Crucial's low end model and I've seen quite a few of them fail in Mac's.

Personally I would replace it with a Crucial MX model, a OWC Mercury or a PNY CS900 SSD.

Yeah, your harddrive is failing again I am afraid. Make sure when you replace it to replace it with a ssd that is compatible with use in an iMac

And you might also want to review your apps and unsigned files, apps with heavy CPU usage in the background can also make your computer sloppy in use

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these articles:  Pubic VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).    

Additionally a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

Check the read and write speeds with Blackmagic Disk Speed Test 4+. It's available at the App Store.

You can get an external SSD in its own enclosure and achieve speeds in the range of 2500 MBs. If you have budget concerns consider this setup:

It's slower, 500 MBs, but I've used it to boot from with an Intel 2017 iMac and it was as fast as my internal SSD.

Just some food for thought.

Dennis Longnecker wrote:

Mr. Allen - You are a genius! I made this change last night and let it soak all night. Today things are so much faster.

Reports now say my performance is good. Write speed is 433 MB/s and read is 520 MB/s....which is better than my test this morning! I'll run it tomorrow and see how it behaves.

Dennis

You are most welcome. When this happened to me after I did an SSD upgrade, it was the amazing Grant Bennet-Alder who walked me through my issues. He's the real genius.

Your speeds are now within what is expected for an SATA 6GB drive in that installation. For reliably issues, I would still prefer to see the Crucial MX series or an OWC drive, but you are good to go for now.

Regards,

Allan

Please determine if the same problems occur in "Safe Mode": Start up your Mac in safe mode - Apple Support

Please post the entire Etrecheck report using the Additional Text button:

OT, I can see the entire report. It is labeled "LOG" in OP's original post.