RMS Normalize … tends to push tracks into clipping.
Correct. That’s why you follow that with Effect > Limiter like it says in the mastering document.
You don’t have to limit at -3.5dB. That’s just the audiobook standard.
And to keep RMS Normalize from responding to excessive low frequency sounds, you start the processing with Effect > Equalize: Low Rolloff for Speech.
-=-
If your problem is widely varying volumes between performers, you might be a candidate for Chris’s Compressor.
I change the first value, Compress Ratio from the default 0.5 to 0.77 and it simulates the leveling/processing at the local radio station. It evens out volume variations and makes the show louder.