1. Do you prefer to use the same layout on different balls or do you vary?
Most all of the balls I have had with some minor variations essentially used the same layout.
I haven't really ever felt it limited me, I've tried once in a while having a radically different layout. To see if it gave me something different, but I wound up going back to my typical layouts.
2. What in your mind determined the "layout that best works for you"?
Pretty much just experience over time, this worked, that didn't.
Using multiple balls give you a more versatile look. So other than layouts for a particular or unusual situation, Using only two or three layouts is plenty.
Here's a quote from Rob Mautner:
wait for itAll the layout does is to position the core within the ball.
When you use the same layout on multiple balls, you can get a very accurate read on the differences based on the differences between the balls without muddying the waters by using different layouts.
If you want a ball that goes long and snaps, don't buy a ball that hooks early and arcs and try to drill it to go long and snap. I interviewed Tony Reyes a few years ago, and he told me that he had over 30 balls on the truck, and all had one of only three pin positions.