As a physics smell test, TMS seems to be performed using quickly releasing a capacitor to create a 1-10 (order of magnitude) Tesla magnetic field over a very short period of time. 10T is similar to the magnetic field generated by an MRI. For comparison, a toaster produces a 100 nano-Tesla field, about 7 orders of magnitude smaller. So supposing TMS causes real effect, the clippers are so weak in comparison that I would think they are harmless.

In terms of electricity, which people have more intuition about, 7 orders of magnitude is the difference between a studio camera flash and a lightning strike .