Thanks for both of your replies! And for the video ... i rewatched it to refresh my mind.
I will play with fuel rate, buoyancy and curl as suggested. I think bursting fuel rate should help or at least to continue exploring.
The render shown is standard. When I tried XP & Redshift i had really results and haven't had time to watch more tutorials. The previews in XP Explosia looked good, but the VDB with material looked brutal.