What is the best way of grouping lots of raster files (geotiffs)? GeoRasterPackage, Mosaic Data Sets or some other way. I want to add all of them as a single layer to the map. Thank you.
The recommended approach is to use a mobile mosaic dataset. You can create this via the API or using a geoprocessing tool in ArcGIS Pro.
API: Add raster data—ArcGIS Runtime SDK for .NET | ArcGIS for Developers
Pro GP Tool: Mosaic Dataset To Mobile Mosaic Dataset—Data Management toolbox | ArcGIS Desktop
Thank you Mike for the clarification.