When I render/export my project I only hear digital noise?
All Freqport products are real time only. Meaning you have to export in real time. Some DAW'S need a workaround to export in real-time and also some DAW'S doesn't support bounce in place in real-time. Please refer to your preferred DAW'S manual.
Should the AnalogHub buffer size match the DAW'S buffer size?
No, the AnalogHub buffer size is independent of the DAW'S and is in most cases fine to leave at default (500) also the lower latency mode is only for when you record instruments via the FreqInOut units, and want to bring down the recording latency.