From their bet sizing and river raise they look rather fishy, do you have any kind of read on them? If they are spazzy I'd call, if they are weak-tight or passive I'd give them credit for a weak king and fold.

not much of read other than they don't seem like a good reg. E.g a few poor calls or bets but nothing crazy as of yet

I feel like this spot is super player dependent. Vs. some players I wouldn't even feel comfortable calling that 1/3 turn bet (thou I most likely would for the price) vs. others I'm snapping of that river raise. Hard to say what I would do by default but I feel like this river vbet is on a thin side (I like it though) and therefore I'd probably just fold to the raise even though it doesn't make that much sense (I'd just respect the preflop range advantage).

I would probably be checking this back on the river. It seems like we're going to have the best hand a ton but there are a decent number of better hands that will be calling us and not a huge amount of the hands we beat are particularly likely to call here.

When we get check raised here it's very difficult to assign an opponent any kind of range here. I would not expect any of villains Kx to play this way since we are going to be checking back so much of our range as it's hard for us not to have some sort of showdown value here. I think curiosity would get the better of me and I'd click call, but I wouldn't be thrilled about it.

Yeah I prefer checking back also, good to go for thin value but he isn't calling much here that is worse and if we are playing fishy players they may do something like this and we feel gross about it. They will want to slow play their monster or get leveled into bluffing you. Either make it 50% psb OTR or check back IMO

I wouldn't be going for thin value here. QQ-99 is going to check call the flop a ton, so we're kind of hoping he just barreled 8x because he doesn't know what else to do and cries "pot odds call". Too thin imo.

Once he raises I'm having a hard time giving him credit for Kx and would call, but like the others I'm not thrilled about it.

Should usually bet a bet/fold and give credit. Value-betting as actually very reasonable and an ok choice, but it does re-open the action and we sometimes have to deal with the consequences. This can sometimes be enough to make a value-bet on the river -EV even if we expect to have over 50% equity vs his calling range. So underbets on the river /especially and solely with position/ needed to be treated with caution. As such we probably might find that value-betting here doesn't improve our EV that much at all making checking a perfectly reasonable alternative carrying probably similar EV (but it of course depends on villain's propensity to ever bluff raise).