I've had the chance to try Risen 3 Titan Lords Enanched edition with and without boost mode.
The game runs with unlocked frame rate and vsync on.
On a regular PS4 it runs at 30 fps with frequent drops to 20 in some areas, and very rare 60 fps peaks when facing a wall or the sky.
With boost mode it runs just a little better, 30 fps with less frequent drops to 20. I've tried (with boost) the same areas where it drops to 20 (without boost), and in some cases there weren't drops at all, in other cases they were less severe.
That's it