but my volume is super loud.
Just by listening? Doesn’t count. Does the MP3 still pass ACX-Check? That’s what ACX is going to be evaluating.
And yes, do everything in WAV or Projects and only produce the MP3 as the very last step before shipping it off to ACX.
Have you submitted a test yet? ACX will allow you to submit a short test to make sure you’re on the right track. Scroll down. That post is in two parts.
It’s a new user mistake to read a whole book and only then stop to find out if everything is OK.
There are non-recoverable reading errors. For example, once you have overload or clipping damage, that’s the end of the reading. ACX will fail you if you got to technical perfection with heavy corrections and filtering. The failure is “Overprocessing.” Nobody is going to pay if your performance sounds like a bad cellphone.
You can submit a test here on the forum for evaluation of common errors.
https://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html
Koz