Just uses alot of your RAM, you can do tiled rendering if you run into memory issues down the line. But to be honest 16k is HUGE. if your rendering at 2048 pixels across no texture resolution should be much bigger than 2k and thats at close up.
TEX is the same as tiff by the way, just a format made to work with render man, but also works with other renderers.
Tiff is a strange format, its not one size fits all it comes in many different flavors. TEX is a good to use as its still tiff but it will ensure it behaves expectedly.
I like taga too, its nice and simple.
FX supervisor - double negative