Sometime in the next couple of months I plan to add a sump to my 10 gallon and I had a couple of questions

First, is there any benefit or negative side to using flexible tubing over pvc? Is one better than the other?

Second, when I'm looking for a return pump, if the return pump is more powerful than the overflow (200 vs 330) will a ball valve help this? How will I know what to adjust?

Third, when I'm plumbing my return line, I do not want to drill any holes, do the locklines just bend over the top of the tank, or is there a way to secure them to the tank without drilling? I've seen some people use pvc and just have it hanging into the top of their tank but I'd rather use lockline for the look of it.

Thanks for the help!