Too many variables here
Flowing water or calm?
Casting or dropping over the side?
What species?
What type of bait?
Braid or mono?
Windy or still?
All of these affect what type of float I use. I've used floats from pea sized to large enough to suspend 2 oz of lead on line from 1 lb to 35 lb in styles from stick floats to round and snap on to line through, ocean and freshwater. I have an entire tackle box of floats, weights, and hooks for different applications depending on these and other variables. Now for the standard situation for walleyes on the Sheyenne river with very little wind, I use is a ML, 6 ft, fast action spinning rod spooled with 10 lb pp braid. For the float I use a line through hybrid between stick and round shape using a string type stop. I use a larger float and more lead than most as I need to get down to the bottom fast otherwise the float goes downstream to fast before getting the bait situated and it turns into an exercise in casting and reeling instead of fishing. I prefer a small jig over a plain hook as the turbulence in the river will blow a plain hook and bait around more whereas a jig tends to keep the bait closer to the bottom where I want it. If there is some wind, I have often used a weighted float to help with casting and line drag which can really mess with a floats efficiency. I, as well as others, can probably give you some other suggestions if you can provide some additional info to the variables above. Hope this helps.