I think this is a snapcall because he has so many missed draws in his range that need to bluff the river. I wouldn't expect him to raise them on the flop because you have a more overpair heavy range and he can credibly rep 88-JJ and 7x on the turn by calling the flop and betting the turn when checked to. 

I don't know why you would think he has a lot of Qx in his range and I don't see him having too many 6x either. He probably doesn't have too many pure floats because of position and the SB. Also, Qx is unlikely in his floating range because it doesn't have any backdoor straightdraws. 6x is unlikely because of how early position both of you are.

There is even merit in betting this river to get value from 88-JJ and 7x. We can have several missed draws by the river. It's probably player dependent on whether betting or checking the river is best. By checking we likely miss value from almost everything worse, but we can bluffcatch vs his missed draws. If you estimate his range on getting to the river and frequencies for betting worse for value and bluffing, you could calculate which is higher EV. It would require a lot of assumptions about the average player because we have such a small hand sample. 

As played, I like shoving this river for value because it is one of the strongest hands we can have in our range other than turned 66, 77, and turned Qx. Like I said before, we will have a lot of missed draws so adding in thinner value hands like AA, KK, and JJ will help balance our river betting range. I would also bet a bit bigger on the turn in order to bet around the same % of the pot by shoving the river. 

Given the position you opened from and your double barrel, ace high has very little showdown value. How much air you end up with on the river heavily depends on how wide you open from UTG+1 pre-ante and how frequently double barrel the Q turn. If you don't have hands like 89s-T9s and non-nut broadway clubs in your opening range and don't barrel turn without at least a draw then you are going to end up with very little air on the river. Thus his AcXc has very little showdown value. With that said, it would be hard for him to expect to fold out better with a shove.

Whether he bluffs river with AcXc depends on what lvl thinker he is. A lvl 1 thinker might think Ace high has a lot of showdown value, a lvl 2 thinker might realize it doesn't vs a tight opening range and bluff, and a lvl 3 thinker would know it doesn't have much showdown value, but not expect you to fold better by shoving. 

It's not a float when he calls flop with clubs. It's considered floating when you call with little or no equity. Such as backdoor draws or a weak gutter. 

He can have QcXc, but there are only so many combos of that. Three combos: AcQc, KcQc, QcJc and maybe QcTc if he is looser. There are plenty more combos of worse pairs: 6 combos of JJ-88 each. He ends up on the river with 7 combos of better hands and has 24 combos of reasonable calling hands. Sounds like an easy VB to me. 

I doubt villain calls turn with 55-. I didn't notice that we have the Kc so that cuts out one combo of better hands. Do you guys think it's more profitable to VB or bluffcatch river?

Well it would be pretty much suicide for him to bet much worse than KK for value (maybe JJ?). The whole point of checking is to induce bluffs from missed draws.

It doesn't have to do with what % of players are going to bluff shove, but how many combos of air villain ends up with on the river to bluff shove.