When you normalize the RMS “loudness” that should work for perceived loudness but it often pushes the peaks over the ACX spec, and often over 0dB into clipping.
The general procedure is to limit after RMS normalization.
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Any linear volume boost will also boost the background noise. If RMS Normalization ends-up boosting the RMS levels by +3dB, the peaks and the noise floor, and everything else will be boosted by +3dB.