How to get the most "umph" out of lipos

[marshmallow]

Hi guys, just wondering if anyone has any tips or tricks on how to get the most "umph" out of lipos. I have seen people charging at stupid amps like 20 for example, does this effect the output of the lipo? I have seen other people having to run there cars down before a 12th scale final because they have more than the BRCA voltage allowed before a final. Is this just for safety or will more voltage increase the power?