The only reason I bought a round head for one of my Ad200pro strobes was for it to fit specific modifiers for a certain look I was going for. But honestly, most modifiers don’t need a round head to work. And once you modify your light, the shape of your catchlight is determined by your softbox, umbrella etc.
Tagging on to your comment because you’ve covered most of it here.
In addition to getting close to your subject, if you can find an angle to shoot that maximizes the distance of the subject to their background, that can increase subject separation which also helps perceived sharpness.
Jan WegenerJan Wegener has a great video on sharpness that talks about some lesser-considered factors in perceived sharpness.
Only one? Of what I own? 50mm f1.2
Of what’s currently available for my system? 28-70 f2
Though what is interesting is that if I am able to have multiple lenses that completely eliminates my desire for the 28-70. Too heavy for a single lens.