Pelias is pretty difficult to use with the kind of automated config I'm hoping to have for this project but I might give it another go.
OTP is actually really fantastic and it might be a better choice than valhalla's multimodal especially if it can handle GTFS realtime. Thank you for the reminder that it exists!!!
If you only want routes without multimodal you can use Graphhopper https://www.graphhopper.com/
Or alternatively OSRM? https://github.com/Project-OSRM/
For a single solution to geocoding and autocompletion, there's Pelias: https://pelias.io/