There are 2 different knots both called FG.
I use the single mono version ending in 7 or 8 half hitches like Charlie. It's really strong and thin. I'm pretty quick tying it now but if I was wrecking for instance and need to re- rig fast I'd use a double grinner/uni.
One thing about braid to leader knots they are subject to wear on the braid and it's not always obvious, particularly when using lures. It pays to cut them off and strip back a metre or two of braid and re-tie fairly regularly. It can seem like a waste of time until that is the braid gives way under surprisingly little pressure. This particularly seems to affect whiplash, probably because it is so thin to start with.