As for your other question -> "Why ASM password file is important if we dont use flex asm" ?
What do you mean?? Where did you find this info? How did you decide it?
In FLEX ASM, password file is also important.
Oracle Database 12c creates an ASM password file that the clients will need to authenticate..
Read this ->
http://www.oracle.com/technetwork/articles/database/asm-odb12c-enhancements-2206102.html