you can have em all on. you can turn em off selectively. heck, you can get picture-in-picture. 'normal' view, thermo, and ultrasound, with room left for the smartgun to show ammo count.
The only time you want to use a selective type of view, would be if theres too much glare to compensate for, or something similar. using only thermo is good, if you want to check how visible you are in that spectrum.
Cybereyes(Rating 4)[flare comp, low light, thermo, smartlink, mag, VE 3, ultrasound sensor] alpha, 0.4e,
33,500 [15/16] is my own recomendation.