Preserve sources before balancing
Start with copies of the original files and label each track's role. Keep voice, music, ambience, and effects separate so the arrangement can be revised. Decide which sources should run continuously and which need a defined start. If channels need rerouting or the format is unsuitable for the next system, use audio-channel-routing or audio-convert instead of hiding the problem in a level adjustment.
Match the operation to the arrangement
Use audio-mix for the ongoing relationship between multiple tracks. Adjust the primary source first, then add supporting tracks while listening for masking and leaving headroom. When a clip must begin over an existing base at a known point, use audio-overlay and confirm the base remains present.
A crossfade is a transition tool, not a universal fix. Use audio-crossfade when one file should hand off to another and the boundary would otherwise click, gap, or jump in level. Do not use it to hide a wrong start time or an unbalanced simultaneous layer.
Accept by listening and checking peaks
Listen to every overlay and crossfade in context, then listen through the complete output. Check peaks against the delivery ceiling and lower contributing tracks if the mix clips. For a broader episode process, connect this focused stage to podcast-recording-editing-delivery; segmentation and noise reduction remain separate jobs.