That is correct. Bewildering really.
The proper name for it before some egghead at Epic went with flesh is Soft Body.
The plugin being beta is probably the reason behind most issues.
What you have resembles a cloth simulation almost entierly.
This either means that your “flesh” definitions are incorrect, or that the solver sucks.
Or both…
The behaviour on the right would lead anyone to believe the solver sucks.
Shimmering like seen there is caused by moving vertex up/down every tick.
On a soft body the verts should never really exceed a maximum distance defined by geometry - they clearly are in that case…
The lagging is probably due to these calculations missfiring and pushing the vert around every frame.
More vert in the mesh will mean more cpu load - and more GFX load.
My guess is that the current state the solver is in bottlenecks your CPU before it even reached the GFX.
You can test with the profiling tools to know for sure. But other than knowinf it won’t fix anything.
On one hand, I’m glad they are trying to make Soft Bodies a thing (a feature epic has lacked forever).
On the other, between the engine not working at all, and Chaos being a hinderance on performance that has most projects revert to physX I really, really doubt it’ll become useful for anything but movie rendering…