There are thousands of compatible charging stations all over the place. The issue isn't finding a place to charge a Bolt, it's that it takes longer. Teslas have dual chargers built in, each capable of higher amperage than all other electric cars, so at SuperCharger stations you can charge your Tesla at a much faster rate.
So in both cases, you have to plan your trips around finding charging stations (which isn't hard in most areas), and you'll need to plan time to charge -- but that charging time will be less with a Tesla. And THAT is the advantage of the SuperChargers.
That said, there is no guarantee that Model 3 will have dual chargers. It may very well be that while you can still use SuperChargers, it will take as long to charge as it would the Bolt. Tesla is making a lot of cost saving decisions with the 3 and until we know for sure, we can only guess at it's charging capabilities.
Oh, and a couple weeks ago I took the Bolt on a 4.5 hour round trip, mostly highway. I still had 61 miles range left when I got back.