Its not just the line...you have to consider the rod & reel you are putting it on.
In the bay I used a light 6' spinning rod with 6 # braid to cast 1/4 to 1/2 oz jigheads. If you put 20# line on that you would lose distance and probably break the rod or reel trying to get unstuck.
There is really nothing in the bay that can't handle...even a 10 bluefish...but that is fun ride...
Next size up is a 7' medium/light spinning with 12#. That lets you use heavier lures and fish deeper. You could substitute with a baitcasting with 20#.
Next up is a 7' medium conventional like a Penn Squall or a shimano tld 15 with 30# braid. That is the go-to all around outfit for bottom fishing, drifting fluke deep on reefs, livelining bunker, trolling plugs & mojos, and jigging diamond jigs from 4 to 12 oz
The only time I go overweight on the braid is that I have 65# on a Penn International 50W for tuna fishing