Congratulations but it sounds like you're trying to justify your old iMac and the fact that you didn't/couldn't wait by complaining about iMac 2020. The important thing is that you're happy but I don't recognize most of the problems you're mentioning and I've read and watched most reviews and threads here. I even created this thread
https://forums.macrumors.com/threads/imac-2020-reviews-and-benchmarks-the-last-intel-imac.2248978/. I think even you wouldn't say no to a better iMac if you could have waited, specially when the base model has a better GPU than last year's top model (5300 vs. 580X), but like you say you're a light user in no need of a better iMac.
Throttling: It's the first time I hear about this since no one has mentioned it in any reviews, benchmarks or here. The fact is that iMac 2020 gives the best performance since it can use more watts than previous iMacs. It's not crippeled like previous iMacs in that matter. The 8-core actually clocks higher than specified in tests (Max Tech), 5.1GHz vs official 5.0.
Heat issues: iMac 2020 gets hot but not hotter than other iMacs or Mac mini. Apple has always prioritised low fan noise so all iMacs and Minis get hot up to 99 degrees C. Haven't heard of any other heat issues.
Fan noise: This is a subjective matter. Some people are more sensitive than others and want their iMacs be dead silent even under heavy load. Those complaints are often about the 8- and 10-core iMacs, the most power hungry CPUs. Of course they get hot under heavy load and make the fans spin up but it's not anywhere near "hair out of place" levels. On contrary in many reviews the fans stay quiet or just "whisper" under heavy benchmarks.
Since you're a "light" user you wouldn't experience any of these issues with iMac 2020. That may be the reason you don't experience such issues with your iMac 2019 either, but under heavy tasks you may also experience all this if you pushed your iMac.
The only real problem is the 5700XT graphical glitch that hopefully will be solved by a driver update.