The Bright Way is ambiguous regarding the existence of what humans would call angels. The current prevailing opinion is that they must exist in some form or another, since The Light itself is utterly unknowable and inapproachable, any interaction between The Light and its little ones must be made via a Metatron-like figure, not by The Light itself.
Regarding demons, the Bright Way has taken a consistent stance of “It's best not to think about it.” If demons do exist, then fixating on them will only bring trouble. If they don't exist, than you're wasting energy fretting over nothing. Unlike the dearth of popular piety surrounding angels, there is a belief among the particularly superstitious that the Underlay is either The Void itself (Hell) or is infested with demons, meaning that the yinrih have been routing their FTL communication through the realm of the damned. This view is roundly rejected by the Claravian Magisterium. Those who believe this idea say that the only reason the Bright Way dismisses their claims is that, since the Bright Way itself discovered the Underlay and invented the ansible, that it would make them look bad if it turned out the interplanetary civilization they largely helped build was piggy backing off of hell itself.
This superstition only worsens after the invention of the mass router. Now it's not just information, but people who are traversing the Underlay, opening the door to ideas of demonic incursions into realspace via the mass router network. Humans absolutely eat this up, some seriously, others in jest, as the idea that hyperspace is actually Hell is a recurring theme in Terran sci-fi, as can be seen in Doom, Event Horizon, and Warhammer 40000.