Weren't you yourself searching for the fastest Ferrari when you purchased the 2019 iMac? You could have easily purchased a 2017 model for what you use it for and you would have seen zero difference in performance. You chose to go with the current model, because it was the newest one and you wanted/needed one.
So I don't really know why you would be happy that you purchased the 2019 model, because if you would have waited a little longer you would have got a much better machine on every front. Faster, better speakers, a much better camera (which is more important now than ever" and the option for a matte screen (which isn't for everyone, but my god I love it). Oh and you could have gotten all of those things (minus the matte screen) for the same price as what you paid for for you 2019 model.
And for the record, I've not seen any of those issues you've stated are happening to other 2020 users. Mine is quiet as a mouse and runs very cool. It easily the best iMac I have ever used and it really runs beautifully.
At the end of the day there is always something newer down the road. Trying to justify within yourself that you made the right decision by buying a little earlier than the latest model is normal human behavior. You have a good model iMac for sure that as long as it works for you, that's awesome. But trying to justify it against the 2020 model that is superior in every single way is just silly.