I understand you.

Personally I put all of what you've mentioned and some more stuff in a blender and mix my trainings up quite often to keep things interesting.

The interplay between the active rest recovery within HIIT and steady state exercises alternate stimulatance for both your brain and muscles.

I also alternate with stepping back and forth between sessions (if the space permits). Sometimes listening to podcasts, other times just nothing. Ocassionally (but not much, I feel like music).

As for creative writing ideas. For me it works best when I step around in quietness between sessions, on a light pase on the treadmil, or (even better) outside in nature.

Idon't know about you, but for me when I walk for about 20 to 30 minutes, that's my sweetspot to trigger enter a great flow state.

Thrive!