I have an Asus strix B450-I Gaming with G.Skill Ripjaws V 3200 CL14 and a 3700X. I ran into the same issue when activating the DOCP.
I had to clear the CMOS and let the PC boot with the RAM @ 2133/1.2V then go into the BIOS, select DOCP and iteratively manually set the memory frequency at increasingly higher frequencies, starting from 2400 (voltage 1.350). I had to use a small increment eg +66 or +133 MHz at each iteration otherwise the PC would not post and I would have to start all over again. I can reach 3400 14-14-14-34 but decided to keep the RAM @ 3200.
I left everything else on default settings for now, temps are all over the place (50 - 55 idle, in a Dan Case A4 with the Asetek 645 LT AIO) but I adjusted the fan curves. Running the latest available BIOS (Asus 2602 / Agesa 1.0.0.3ab) and AMD drivers. It's stable but of course I'm not happy with the temps (Cinebench R20 reaches 88 degrees, in games it's 78-79 degrees).
Anything I've tried around deactivation of PBO and XFR, undervolting, limitation of the TDP etc... in BIOS or RM has not yielded any significant improvement.
I'm waiting for custom cables to arrive, then I'll rework my cooling setup to see if I can gain better temps. In the meantime, I run with default BIOS settings except RAM profile and fan curves. I have Windows on Eco power plan and AMD Ryzen Balanced. All the monitoring software (HWMonitor, HWInfo64, GPU-Z, MSI Afterburner and even Ryzen Master) seem to activate the cores somehow and cause temps to rise and fans to spin up to counter that.
I also have a MSI B450i Gaming Plus, the situation is also pretty bad with that mobo, although not as bad as with the Asus: idle temps are at 44-45, XMP worked immediately but it exhibits the same behaviors, just with slightly lower temps (perfs are a little bit better as a consequence).
