Never folding here, only concern is how to get V1 money.
There are so many hands that can be raised on a flop like this.
If he is competent V could attack this board and a donk bet with flush draw, a gutter, A
x, 9x and so much more.
Way more combos that attack with a little equity than the 3 combos of 33 (he should never have 99 here if he is good). If he has that, so be it. Reload and on to the next hand.
Tank calling and leading turn vs shoving seems the real question.
tank calling and leading turn:
pro - we keep V1 bluffs and semi bluffs in.
contra - we dont protect our equity and we could lose value against hands that get scared by turns (really not a big concern here)
shoving:
pro - we protect our equity
contra - we fold out all of his bluffs that have very little equity
With these two options I highly favor flatting and evaluating turns.