I would be looking at a huge range of factors ahead of hosted vs reference like:
- How many features are trying to render in the map
- How complex is their geometry? Like does a straight line have lots of vertices? Geometry errors?
- Are any transformations or projections occurring between the database, service and map?
- Are layers editable?
- Is symbology complex? Can you basic, non-expression driving symbols, and lighter icons?
- Service types e.g. can you use vector tiles, map services, anything but feature (if you don't need the interactivity)
- Reduce number of features and apply filters at a service level, not on the map. Don't use relative filters like date is within a week.
- Remove unnecessary fields.
- Turn layers off by default, if not immediately required
- Use a vector tile basemap over imagery
- Turn off download of attachments on some layers
There could be some merit to one layer causing individual problems so you could explore that by:
- Testing one layer at a time in a new map
- Testing removing one layer at a time in an existing map
- Watch the network traffic in a desktop browser developer console. Which layers take the longest to display? Which ones are the largest? Should be same in browser as field maps.
You can look at specific services more deeply when you know if there are some in particular.
For field maps you can:
- If going offline, turn on airplane mode if you are drifting in/out of connectivity.
- Turn off auto sync
Watch some Esri UC videos, read blogs e.g.
https://mediaspace.esri.com/media/t/1_tnz29jc6
https://www.esri.com/arcgis-blog/products/arcgis-online/sharing-collaboration/best-practices-for-hig...
https://mediaspace.esri.com/media/t/1_y2v320tn
It will be difficult for support to troubleshoot something like this particularly if you're pushing the thresholds of data in a map. Likewise a bit difficult for us to be specific unless you can narrow it down to a particular service or layer...
