well cooling the gpu is the main priority for my system temps for the gpu's I have them at a stable 65C and the fan speed @ 65-70 % I am very comfortable running them for 24/7 use
but as for your question if the card itself has an array of fans it will suffice for keeping things cool for cpu i use aio cooler work best imo stock fans are more than enough but there is no set number of how many to use of course the more the better I hope this helps to answer your question feel free to ask for more advise if I can help :)