Based on my experience and in the past competition with BitUniverse, the winner with the highest APR is doing the efficiency trick, which is trying to catch every single bottom and top of the candle
You need to look at the pair movement, in what scale it usualy moves. 3% a move? 4% ? or even it fluctuates very highly in the small scale 0.3% ? The best trades is always the most efficient grids number vs price range.
Analogy if price coming from 1000 to 1500 in one swoop, you better had only 2 grid at 1000 and 1500 and profit 50%.
But if it takes time and really high volatility from 1000 to 1500, you can use higher number of grid and try to catch the movement hopefully the volatility will yields more than 50%
To compare on your own, you can try to create the bot with same price range but different number of grid. Let it run for couple of weeks and let the result shows you which one is better for you