Most exchanges match by price-time priority: best price first, and among equal prices, earliest arrival first.
Queue position is a real asset. First in the queue at the bid fills on small trades and can cancel if the market turns; last in the queue fills mainly when the price is about to go through you, which is adverse selection. Cancelling and re-entering forfeits your place, so adjusting a quote has a genuine cost.
Reading it. Depth indicates resting liquidity - useful for estimating impact - but it is cancellable intent, not commitment, so it predicts direction only weakly.