Agreed with the above except coming from saltwater I used more braid and less backing but there was a real chance you hooked a fish that would dump 75-100ds on its first run. I always put just enough mono backing to cover the spool completely and then filled the reel with braid. If you don't use some mono backing, the braid will slip on the spool unless reel manufacturers have caught up and started to do something to prevent this like Penn did a while back.
For the line-to-line connection to you leader, I would tie whatever you are comfortable tying perfectly... every single time. A double uni is what most people start with and it is a perfectly fine knot. One that I have caught hundreds of tarpon with. You'll want to double the braid side of the knot.
If you are tying long leaders you will want to learn the Albright, Alberto, or something similar. I know many who use the FG and in my opinion it is more complex than needed for essentially no added benefit above the Albright.
Hope this helps.