Perception can be misleading. In Thorsten's case, what "looks like" a "ball of clenched knuckles" (or, firm death grip) is actually not what it appears. In Thorsten's case, while his thumb is tucked over his index finger in "fist-like" fashion, his actual grip (contact) on the cue is surprisingly light. Having viewed Thorsten's grip close-up (i.e. when he would try his hand at the SBE 14.1 Challenge, the booth of which I help man and score-keep), I can tell you that Thorsten's grip is not much different than Buddy Hall's grip, which also looks like he's fisting the cue, but is actually just allowing gravity to rest the cue upon the fleshy pads of his hands.
In other words, "what you see" isn't what you think. While it looks like Thorsten Hohmann (and Buddy Hall) grip technique "looks like" a ball of clenched knuckles, it isn't. It just so happens the cue is softly cradled in that "cage" formed by the thumb and fingers, resting upon the fleshy pads of the hands. I got to see this close-up. The only thing different from Thorsten's (Buddy's) grip from X.T. Pan, is that Thorsten's hand is a semi-rigid "cage" around the cue (but with the cue resting in there), whereas X.T. Pan's grip allows the fingers to move about and freely reposition through the cycle of the stroke.
One should try both. Indeed, in my pool-playing life experience, I've tried all manner of grips (too numerous to enumerate here), and the experience is golden. I'd finally settled on what looks to many like a "fist o' knuckles" (cage) grip that is actually very lightly cradling the cue on the soft pads of my hands. One could argue this is because I play 14.1 and one pocket as my main games of choice. I don't know if I agree with that. I just find that I get a lot more sensory feedback from the cue if I have stable non-changing/consistent contact with the pads of my hand, rather than an ever-changing-grip-through-the-cycle-of-the-stroke as in X.T. Pan's.
Everyone's mileage may vary -- the key is to make the trip in the first place.
-Sean
Well observed buddy

Hope you re doing great Sean-
lg from germany,
Ingo