Maps for free is using Open Street Map. With QGis you can pull OSM tiles using the QuickOSM plugin. You'll have to install the program then download the QuickOSM plugin. https://plugins.qgis.org/plugins/QuickOSM/ And install that. From there you can pull out any information from the OSM database using Overpass queries. This is probably what you'll be best able to use as a base for your map that has the huge scale and flexibility you have in mind. If you don't know how to work with it I can be commissioned to help. But it sounds like you're interested in tackling this project yourself!