I have Yelp installed and also Komoot on the 520+ and iPhone. Komoot lets you route to a specific location or address then sync it back to the 520+ so it works similar to navigation on the Wahoo Elemnt. You need your phone to lookup the address but the sync works.
Besides that, I also have a vPower virtual power data field installed since I don't have a power meter.
I don't find them slowing down the device at all since they only run when you open the apps.