First analyze the files and when burning use the "Apply Cross-fade and DSP effects" option and enable DSP Studio > Volume Leveling (aka Replay Gain) in the burning DSP options (the playback options are not effective when burning).
You can use the "Adjustment > Automatic based on current playlist" Volume Leveling option to make each disc as loud as possible without causing clipping (Replay Gain will usually reduce the volume level - more or less, depending on the source material).
You may want to prepare a playlist for each audio CD. For example, make each list less than 80 minutes if you have such discs (= 700 MB in data use).
EDIT
Attached a screenshot.
Log in to the forum if you can't see the attachment.