Are the maps the same for different devices?

Just a very basic question just for the sake of understanding.  I watched a video where I think the creator said that he preferred to install maps to devices using Basecamp rather than Garmin Express.  That makes sense to me, if it means that you can install the map once to Basecamp, and then install from Basecamp to multiple devices.  That way, you wouldn't have to download the whole map again each time you install to a different device.

But that implies that I could install the same map, for example, from Basecamp to my Nuvi 50, my 2689LMT, and my Drivesmart 66.  Is that true, that the maps are not "device-specific"?  

Of course the devices have different internal storage capacities, and I've seen how Basecamp allows you to select the regions that you want to install, to fit within the capacity of a given device.  Or as I've seen in a video, how you can install maps to separate gmapsupp.img files on a MicroSD card.