How to acheive the same volume on all of my commentaries?

It’s not unusual to smack into peak problems when you start messing with volume.

The AudioBook process also uses RMS Normalize and for the same reason, but follows it up with Effect > Limiter to keep the tips of the blue waves from going higher than 100%.

ACX AudioBook has very strict rules for submission quality and use can use those tools for your work, even if you don’t use the same settings.