SQL & PL/SQL

Hello everyone!

I'm re-writing plenty of functions from PostgreSQL to ORACLE and I was wondering about functions performance. I've read in the documentation plus on the web PIPELINED clause would help about increasing performance.... But I have some doubts:

1) if I mention also PARALLEL_ENABLE clause without partitioning, would that improve somewhat function's performance since I read it would allow the function to be processed in user's memory area instead of the server's memory area?

2) if I do also a CREATE INDEX on functions, especially to ones which are called from other functions or SQL SELECT like SELECT * FROM (functionname(..)), would those Indexes improve something about performance?...

Thanks to all!
Ciao!
Luigi