I think Scala goes too far from simplicity, like its syntax. For example Martin Odersky wrote the method in his book :
def calculate(s: String): Int =
if (
"If the method grows it becomes very painful to read the code". I think part of the answer is that methods should not grow. The functional programing style is to have many small methods.The calculate method is already on the large side.
To answer the more general questions about style guides for Scala programing: Here's a representative example.