The Renderer can operate at 48 or 96kHz. Master files can be created at these rates and stored for archive purposes but are then sample rate converted to 48kHz for encoding purposes. Keep in mind that when working at 48kHz the renderer supports 128 input channels (10 bed only + 118 object/bed) while at 96 kHz 64 input channels are available (10 bed only + 54 object/bed). 

Starting with 48kHz, 96kHz (or higher) sample rate source content will yield better results that upsampled content.