GFCI for electric floor heat
I would not put a GFCI breaker on this device. Code requires it to be GFCI protected and 2 GFCI devices can cause trouble in resetting.
I ran into a issue with one of the floor style that ran a self test that would trip the breaker so we could never reset it (the home owner called me I megged the heater and it was good so then I pulled 1 lead to the heater still tripped the panel breaker, called the mfg and they told me it was in there GFCI test that was tripping the circuit. I believe this test was the end of life test where it basically megged the circuit prior to energizing looking for leakage that may not show up on a standard test until wet.