You're getting FPS fluctuations from IF error correction caused by an unstable FCLK and/or insufficient spreads of CLDO VDDG IOD and VDDG CCD that is reducing IF signal SNR. Incorrect CLDOs for the SoC voltage and FCLK frequency can degrade SNR and cause non-verbose error correction on the IF link between the IMC and CCD, this will cause stutters whenever error correction is present on the IF. You can either reduce the FCLK/MCLK so you can run auto CLDO (noob method) or you can do a manual binary search of VDDG CCD and run DRAM read bandwidth tests with different CLDO CCD values until the number comes to a peak (competent method).

CLDO VDDG's are problematic on AMD and they often sabotage otherwise good system builders when this problems crops up at high FCLK/MCLK. Per Sampson, AMD is working on adding automatic CLDO tuning functionality to Ryzen Master to help people unfamiliar with tuning on AMD to reach higher FCLK/MCLK stable without error correction kicking in and causing FPS fluctuations.

Stabilize the FCLK/MCLK by either reducing them until you can run Auto VDDG CCD stable, or work on dialing VDDG IOD/CCD in until DRAM bandwidth peaks and there are also no WHEA 19 errors present in event viewer. Correctly tuned, the error correction stops, the FPS fluctuations go away.

Granted, tuning AMD correctly is a PITA and it's way more time consuming versus Intel, but this "AM dip" thing you talk about is not actually a problem inherent to Ryzen, it's due to IF error correction caused by incorrect CLDOs in relation to the SoC voltage and FCLK/MCLK frequency.