As i said, internal wing structure decides where your pylons under the wing will be, not necessarily the wingtips.
J-10 has a delta wing. This, in addition to the relative behaviour of leading and trailing wing section design, to a certain limit negates the wingtip effects that you see in conventional sweeped trailing edge wings like Su27. Gripen, for example still uses wingtip pylons to decrease the drag further( saab designers are crazy for efficiency), which allows it effectively supercruise under certain loads.
In commercial jets, wingtip vortices are countered with wing fins.
Depends on how much your wing drag profile is weighted by the vortices.
Any design characterisitcs has pros/cons.
Western jets like F15 have no wingtip pylons due to designers feeling it will add too much stability and inertia and effect its performance in a A-A scenario. It all depends on what performance characteristics you're trying to squeeze out of the airframe.
So in essence, vortices increase maneuverability by destabilizing the plane but also increases drag, so some designers that wanted more efficiency might want to suppress the vortices generation and those that wanted maneuverability vice versa? did I get the reasoning correct?
p.s. super off-topic, but do you know what is PLAAF FOD tolerance standard? Is it closer to NATO (smooth runway and little to no FOD) or Soviet standard (basic runway and FOD tolerant)?