Some temps for the 3700X (boost disabled) with L9a, extra exhaust fan and cardboard shroud:
Idle/light work: 40~45C
Gaming: 50~55C
Prime95: 60C (80C+ with boost enabled)
Running it with boost enabled can cause extreme temp jumps during light workloads, which I didn't like. With the gimped clockspeed the PC is completely silent unless it hits 60C or the HDDs are spinning.
The chipset fan was previously the loudest part of the build, but with a bios update from Gigabyte I set it to silent profile and haven't heard it since. The NVME runs a bit hot 50-55C since it's wedged between CPU and GPU.
The GPU also runs hotter than I'd like (50C+ idle, 60C+ gaming) but still reasonable. Next year I'll upgrade to something with a bigger heatsink and 3 fans.
It's a leftover from my previous build (i5 4690K), where it idled 20C cooler. The i5 itself idled only 10C cooler, and it was watercooled with a 120mm AIO. Load temps were similar between the two builds. All things considered I'm surprised by how well this chip works with such a tiny cooler and case. This build is half the size and weight of previous (Cougar case), and much quieter. Pretty happy with it.
EDIT: Forgot to list parts
Case: A4 SFX v4.1
Cooler: Noctua NH-L9a (intake, with ghetto duct)
Fan: Noctua NF-A9x14 (exhaust)
Board: Gigabyte X570 Aorus Pro WiFi
CPU: Ryzen 7 3700X (undervolted)
GPU: MSI GTX 960
RAM: Corsair LPX 32GB @3200mhz
PSU: Corsair SF450
Storage: Corsair MP510 1TB NVME / 2TB WD Blue / 5TB Seagate Barracuda
Front USB C port: Can't even use it