Hi,
yes its possible to set the simulation frame rate, on the PhysicsScene you can set the Time Steps Per Second, this defines the fixed timestep for physics simulation. The simulation will to substepping with the given timestep on the Physics Scene:
To speedup the rigid body simulation, most of the time is usually spend in updating back the USD, you can enable omni.physx.flatcache extension to skip USD writes and write to Fabric, that will avoid the heavy writes.