As David mentions in his answer, possibly the greatest bonus from Mobile is actually the bullet
When you make a melee attack against a creature, you don't provoke opportunity attacks from that creature for the rest of the turn, whether you hit or not.
However, you seem focused on the fight against Strahd, and from my experience, Opportunity Attacks from Strahd aren't exactly what you should be worried the most here. From your stats, you have 19 dex and no other odd score, and also you are a half-elf. Monks get a lot from bonus Dex - higher chance to hit, higher damage, higher AC, higher everything. This highly indicates to me that a feat with half-ASI, i.e. +1 Dex, would improve your character by a lot more than taking either a Full-ASI (+1 Dex +1 another thing) or a feat without any ASI.
I don't intend to include much math here since this is not exactly an optimization question, but Elven Accuracy from Xanathar's Guide to Everything, if you have some way to consistently get advantage, brings a decent advantage over +2 ASI (check this question for example What is better early game, dex increase to 18 or elven accuracy for fighter-rogue?). In your case, you don't actually have to trade the +2 ASI because you are already at an odd stat, so you actually get both the bonus.
As another option, if your party chooses to face Strahd only at 12th level, which is possible IIRC, you might be interested in getting +1 Dex, +1 Wisdom now, and at level 12 getting Resilient (Wisdom), giving you proficiency in Wisdom saving throws, which are helpful against his charms and some spells (such as Polymorph), and the missing +1 Wisdom, putting you at full 20 Wisdom, increasing your AC again and some damages.