i use mx4 for cpu, cheap noconduvtive and has great performance as well it comes off very easily with 70%iso ive used mx4 for over 3 years now and never had a problem,
for gpu i ussually use same cause im lazy to buy it seperatelly, but i think for gpu you need non conductive one, i think on silicon base but i really cant remember, recently my gpu paste dried so i had to repaste and since i only had mx4 lying around, so i used that and no problems so far, around 5-10 off max from the nvidias standard paste