You said top 5 list. But you haven't given us the list other than Boerboel. The Mojo Ysterberg Mastiff is a boerboel. You had a Fila mix. the Fila might not be good if you want it to accept company. An English Mastiff might not be good as they probably won't run much on your bike ride.

A great dane is a large dog. it can provide protection. I should be ale to accept strangers if taught to do so. But we don't know how long or hard your bike rides are. The larger the dog the harder it will be on the dog lasting for a nice hard bike ride.