I've surfed the Super Fish in waves from tiny dribble to double overhead. This was the 6'0 and I'm just under 170 cm (5'5") and just under 64 Kg (141 pounds).
With a board that size and width it gets quite hard to get a good carve on the rail when you are going very fast in bigger surf. You've got 3 extra inches in length so that might help a tiny bit more, however the whole shape of it is for smaller waves. It's wide, short and fat with little rocker. It is also difficult to ride this board in sucky (hollow) waves. The rails are quite fat so it's hard to stay in the face when it's steep so you'll end up riding lower down the wave. Plus because of the increased bouyancy you'll often hang in the lip during take off which is bad when it's sucky as you want to get under that lip and get down the face fast!
Also the lack of rocker means keeping the nose out of the water during the drop is harder. You can use nose rocker to turn you in a drop by just angling the rail into the face but this boards got none
This doesn't mean it's a bad board, it's just not designed for those waves. As a beginner you probably won't be riding those types of waves anyway.
It's still an every day board, because most days, in most places in the world are small or mushy. When you need performance in sucky or big steep waves then this board has problems. Of course if you only ride this board you'll get good at riding it in these conditions too, but if you ride a board that's made for those conditions you'll see it's short comings. It's Horses for Courses.
As for fins I don't have much experience with trying out different combinations.
There are a lot of variables with fins and size is just one of them. As a general rule you ride bigger fins in bigger waves or if you are a very big guy. Smaller fins for smaller days or if you are a smaller guy. The M5 or G5 is pretty much the standard fin that everybody rides in everything.