The new Collector for ArcGIS (Aurora) supports vector tile basemaps and this app is currently in beta.
As for support for custom vector tile layers, the new Collector app will support this - but there are currently some issues in the current beta release.
Hope this helps,
Yes, you can side load any tilepackages to Collector and S123 using iTunes (https://community.esri.com/thread/90177). Also check out https://www.esri.com/arcgis-blog/products/apps/data-management/introducing-tile-package-kreator-esri...