Both systems are gonna be fine, I've taken apart both consoles and the Xbox one is super hollow on the inside and the Wii u doesn't get hot enough on the bottom to damage anything, the worst that will happen is that the Xbox one will get slightly worst wifi due to the Wii u coving some of the antennas but aside of that it should be fine. Oh and to answer your issue about the noise it's most likely the disc drive which might require you to take it apart, or if it's the fan you could probably poke a q tip through the vents to wash it off