There's two types of electronic nautical maps: raster and vector. Raster maps are basically scanned paper maps, and contain all the data. When you zoom in, you are basically enlarging the map, it will not show more detail. Vector maps are contructed by a database. When you zoom in, more detail emerges that was not visible previously. Like buoys or reefs...

There is no software method to "find obstructions on my route". If you want to be sure, you need to zoom in at maximum level and follow the route you are going to sail, otherwise there is a possibility of missing out on information.