Do we ever straddle?

Do you understand what a straddle is? It's an extra blind. Why would voluntarily posting a blind ever be +ev?

The only time you should consider it is at a juicy private game where you know you're among the best players. Might be smart to appear to give more action to stay invited.

What about a straddle that is allowed on the button? I play in a game where it is permitted. Last to act.

That is a good point. I would BTN straddle in PLO but not in PLO8. Weak hands just remain weak very often in hi/lo and lack playability.

The game is $1/$3 dealer’s choice. You can button straddle for $6. What 4 or 5 card game should I choose and should I always straddle?

I would take 4- or 5-card PLO and probably always straddle. Of course it depends on a million factors. Say they are very bad in hi/lo games and do stuff like limp a lot assuming no BTN straddle then it becomes very profitably as well.