I've developed a native iOS app using GDAL to manage the vector data, and OpenLayers (in a UIWebView) to display the layers (both raster and vector).
For vector layers, the app uses GeoJSON to communicate between OpenLayers and GDAL. It can use WMTS/TMS/WMS for raster layers.
There is a bit of a learning curve for both GDAL and for OpenLayers. But the ...
As an update, the solution to change temp files directory via the Advanced Settings Utility does not work and is a recognised bug for Arc 10.5.1 and possibly later versions. See the ticket here.
Currently, the only way to redirect the temp files for Arcmap is to change the Windows environment variable TMP. I have verified this works.