We should trust our top pair's strength on a wet board; folding to the final barrel over-folds against a range containing missed straight draws.
Checking is the preferred play with top pair on this texture to protect our range and keep the pot manageable.
Note: Betting here is a slight mistake; top pair with a marginal kicker functions better as a check-back to realize equity and protect our checking range.
Once raised, we have a mandatory call. Our top pair is too strong to fold against a range that includes many flush and straight draws.
The 2s is a dynamic card that completes the flush, but we must continue calling to prevent BB from over-bluffing their missed straight draws.
Folding here is a significant error. On a board where many straight draws missed, Q9 is a premium bluff-catcher that must call to meet MDF.
Note: Folding top pair on the river is too tight; we block some value and beat all of Villain's missed straight draws (like 54, 85, or T8).