I'm seeing a lot of variance in the ratios. Some flails have longer handles, some have short. Some have chains as long or longer than the handle, some have almost non-existent chains. What are the advantages and disadvantages of various handle and chain lengths, and is there an "optimal" ratio?
So to give an answer to your question, if you’re going to use a chain-based weapon, the optimum length is long enough to completely wrap around somebody. And in that situation, you want a fairly light, small business end, not a big metal ball.
So maybe something like a rope dart, meteor hammer, or bolas? I've seen some YouTube videos on meteor hammers, and it looks like one way to use them is by throwing the weighted end as a projectile and using the chain (or very often a rope) to retrieve/retract it.
I agree though, flails as shown above seem like an unwieldy garbage weapon. If I had to use one, I'd want a very short chain on it, so probably 2nd from the left on the bottom row.
