I got around 40-45C idle during summer (35C+ ambient where I live) bot now that it's gotten cooler I get 35C idle. While gaming, it doesn't get hotter than 65C. I got 75C while doing benchmarks and stress tests (Cinebench, Aida64) with stock settings or slightly over 80C with an overclock. That is with a stock cooler, but the one that comes with 3700X and better CPUs is much better than the one on the lower end CPUs. The most demanding game I played was probably Vampyr.
As for motherboards, I can't really talk from experience. I switched from Intel and bought a new X570 board and had no compatibility problems. There is an ongoing issue with slightly lower than advertised clock speeds with the new CPUs, but it is getting better with each BIOS update. Not that you'll notice it while gaming, but if you advertise 4.4GHz, give me 4.4GHz, not 4.35GHz. Oh, and the thing about advertised boost clocks, those are single core boost clock in single threaded workloads. Don't expect 4.2GHz on all cores without overclocking if you decide to go with 3600. But those are just numbers and in the end you should care about fps in games and you can see those in benchmarks.
You also mentioned you'd like to keep the cooler silent. There is an annoying tendency with Ryzen 3000 CPUs (and maybe the older ones, but I can't speak from experience) to boost their clocks while doing almost nothing (browsing, watching movies…) for a fraction of a second. That makes the temps spike for a second to and the cooler needs to catch up. It's not loud but it is quit annoying. And I read online that it isn't just me. You can fix this by tweaking the fan curve in BIOS or by using the power saver power plan in Windows. Tweaking the fan curve will mostly eliminate this but will impact idle temperatures. Using the power plan will almost completely get rid of the issue but it will make the CPU slow to boost when you actually need it so you need to switch power plans all the time depending on what you are doing. I don't know if that will get fixed or whether it can be fixed by a better cooler. It's not a huge issue, but I just find it annoying.
Sorry for kind of a long post but I hope you'll appreciate it. I know I would have liked to know about some of these kind of things before I bought some things i did.
