Sorry if this is 'standard' or whatever, im just getting back into cashgames. Villian is LAGgy...32/21/exponential on all streets. But thats only thru ~50 hands. Hes 3-bet a couple times preflop but hasnt shown down.

Is 4-betting preflop a viable option against a LAG oop with a hand like this? Any other lines postflop i could take? Call or fold river?

Betting pot is his standard CB i think.

Yes, 4 betting is VERY viable since this is a strong hand, but not one that likes to take flops...and especially not OOP. I don't like just calling the 3 bet oop, imo.

Flop, totally fine.
Turn, I like a bet here since he's likely enough on air and too many river cards suck.
River...PLZ CALL!! This looks like a bluff.

The turn looks a whole lot like a bluff. You've shown nothing but weakness and he's pushing all-in on a 4-straight board. Looks like two broadway cards to me. But he could have just caught 87 or 57 or some such crap.

IMO you have to decide on the flop if you think your 9s are the best hand or not. If you think they are, then you have to play stronger on the flop and/or turn ... and as played, you have to snap call this. If you think they're not, then you need to set or forget on the flop.