IO540,
this data is from the T210 known icing certification. I have electric prop deicing on my A36 and this matches my experience. The only part that will ice up on a prop is the inner third and that doesn't do any useful work except keep the outer prop blades where they belong.
I didn't know there was a prop only TKS system.
Icex II from Goodrich is a spray-on silicone liquid good for 25 hours and it is a good alternative for non-deiced props, A small can is over 100€ but well worth it.