Wizard penetration passives and multiclassing

Hello,

I have started the game as a warlock (barb/wizard) and a few questions about the implications of secrets of the rime (+1 penetration with frost water attacks):

- Will it affect other abilities than spells? For example the barb's spirit tornado which states that does frost damage? 

- Will it affect frost based damage from weapons? Like weapons that show a +25% frost damage component or an on crit proc frost attack?

-  is 1 penetration actually worth it?

Wanted to be sure before making my barb a frost barb since respeccing is all kinds of bugged right now.

Thanks!