I don't pretend to have the definitive answer on this age old question. For years I thought 44K was the answer. But in recent times I have done everything I can to harmonize 16bit, 48K for all audio applications on my machine. BIAB appears to have no problem with this (with one exception).
The BIAB-VST, while working, continues to throw error messages regarding a mismatch sample rate. So here is my Audio Configuration on my DAW machine which runs BIAB, Reaper and of course system audio. Maybe you will see something that helps.

Dan

MusicStudents Audio Configuration


BIAB – 2025, Reaper (current), i7-12700F Processor, 32GB DDR4-3200MHz RAM, 1TB WD Black NVMe SSD, 2TB WDC Blue SSD, 1TB WD Blue, 2 TB SK NVMe, 6 TB External, Motu Audio Express 6x6