Guy just joined the table, 5 hands in and he has played 3 of them (including this one), the other two were raise and take. Linecheck?

Id 4b

I'd just x/c river again I think

I would also x/c - A is I think good card for him to try bluff here + plus now he might value bet AK, AJ

fold pre, or 4b bluff vs unknown

As played, x/call the river. He will almost never call you with worse

I thought that those aggro players only picked up AA vs me

What the hell?

1) Folding such a huge hand preflop against someone that may be an aggrofish is burning money.
2) "4B bluff" implies he will fold AK/QQ BVB.
3) He will definitely call with AJ/AK/QJ, probably call most Ax. Will not bet a lot of Ax OTR. Lots of draws missed but nut hearts made TP and will likely check that.

1) What info do you have that makes him an aggrofish
2) 4b bluff implies that we fold to a 5b.
3) We see what happens after he calls the 4b. I would propably cbet a lot of boards. Where a fish probably plays fit or fold.

Hm. A lot of people tend to 3B too polarized so I'm very against 4Bing AQ, because you tend to start just folding people off worse and getting shoved on by better; unlikely you get just called.

Well that is essentially what I am saying when I 4b bluff.

When I get called, he probably isn't a reg

The most important issue here is that he is an unknown player imo. So we want to play a standard game and don't call 3 bets OOP.

My standard game does have some flatting 3Bs OOP, why shouldn't it? Generally players aren't mega strong so you can still profit doing that.

Well when calling OOP you would need to compensate with card advantage or skill advantage.

card advantage vs unknown player: we don't know his 3betting range. When he is polarized we are either behind or way ahead (We 4b our value range so our flatting range never hits the top of his 3b range). When he is merged we are somewhere in the middle or behind. But we don't have any info on this so it is better to play an optimal game and fold or 4b bluff
skill advantage vs unknown player: you could compare yourself vs the general player pool with a 100bb buyin. This has to be your own judgement I guess

When we you see that someone is a fish, we can change it up and call with hands like AQ because we probably have a great skill advantage postflop and card advantage depends on what he 3bets