I don’t know about the pit bull part but English Mastiffs are a pretty good breed of dogs. I have known several and they were very gentle. Pit Bulls are just plain killers. My stepson has a Pit and so far he is just a big baby but I don’t trust him.
You are very wise. Like pet wolves and hybrid wolves the behavior of pit bulls and inbred Rottweilers is extremely unpredictable. They can attack their owners for no reason and should NOT be trusted with children. If you want a big dog that's protective and loyal get an Irish Wolfhound. My IW weighed 175lbs and the one day when two Dobermans came after me he made quick work of the two Dobies (killing them) and then came up to me wagging his tail and I told him he was a good boy.
“I don’t know about the pit bull part but English Mastiffs are a pretty good breed of dogs. I have known several and they were very gentle.”
I has some friends that bred them. The first time I met their dogs they came up and sniffed my crotch. I ain’t no sissy but that just plain petrified me. After that we were big buddies although you needed a raincoat to keep the slobber off.