If I were allowed only one fly for bluegill, it would be a McGinty wooly worm with a really tiny red wool or hackle tail and dark brown hackle palmered over the body. A 1XL #12 hook is about optimum, IMO. I retrieve it just fast enough to make a wake simply by lifting the rod tip.
Very simple fly to tie.
For largemouth in weed beds in lakes, a fly i always did well on was a big wooly bugger with a tail about 150% of normal length. I tied this on a stinger hook (usually a #2, but sometimes a #6 and I would either lash some foam or wind a pretty thick layer of kapok (good luck finding kapok any more..) over the front third of the hook shank and then cover it with the main body material and the palmered hackle. It's ok if it looks kinda pregnant up there with all this material. it's supposed to. This thing sits in the water transmission down and drives bass nuts when it is jiggled.
If you put a looped weed guard on it made out of something like stiff Mason nylon, you can fish it right into the weeds. Or if you put a little weight in the back end, it counter balances the foam and the thing achieves a neutral buoyancy, sinks real slow and and sort of of sits in one place so you can twitch it, etc. Most of the takes come on the drop. The bass just flare their gills and suck it in.
I've caught a lot of nice LMB on this fly, particularly out of Presque Isle Bay. All white is good. So is all black or any combination of white, yellow, grizzly, black, etc. The bass don't care...