Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

my question is simple how do or don't metamagics such as empower/maximize affect warlock invocations and eldritch blasts?

They do not.

Wouldn't make sense anyways, since the whole idea about metamagics is that you have to spend higher level spell slots to apply metamagics. And since there's no such thing as spending spell slots at all for warlocks (and warlocks aren't actually spellcasters), it's just not applicable.

Normal metamagics don't work on warlock abilities. There are metamagics for spell-like abilities in pnp, which work for warlock abilities, but we do not have those on the server.