OpenCL in solver is checked but gpu usage is still very low on a MacOS is there anyway to boost particle sim ?

What kind of particle simulation are you talking about?

More information would be helpful. But in general, Houdini uses OpenCL so your graphics card should work.
You can check in the preferences if Houdini sees your GPU as an OpenCL capable device. If it shows up and GPU is selected then it should work.
If your scene has to cook a lot before it gets to the simulation, then this might be the reason because the GPU doesn't have anything to do until everything else is done.