This is different from UR aggro lists in a number of key ways. It plays a much lower curve. This allows it to function off of just 17 lands and draw business more consistently, but also means the curve is too low to support numerous Snapcasters, Nimble Obstructionists or Vendilion Cliques. Although including any of these cards in your variant wouldn't be wrong, as long as you keep the total number of 3cc spells to under 4.
It plays a record number of conditional counterspells. This is why you absolutely never want to tap out on your turn until the midgame (to play a threat that will close out the game in a couple of turns). This is why it plays zero sorceries and zero Thing in the Ice. You want to only play your cantrips at the end of your opponents turn once you're certain that they haven't played anything that you want to counter or bounce or dismember. Thought Scour is an amazing card here. It routinely functions as a Dark Ritual with a cantrip attached to it. The rest of the list is self explanatory.
My biggest issue with delver is that it incentivizes you to play t1 and then have it survive and either luck into flipping or require library manipulation to set up any kind of clock. At that point you're protecting the queen for 7 turns (long time in modern) to drive home the kill assuming your opponent doesn't have any lifegain.
Play it any later than that and you start brushing up against your opponent seeing significant chunks of their deck and executing their game plan or stopping yours.
Imho blue needs more "free" spells like shoal before this can really become a reality.
You may still occasionally win when you can snag something pivotal like a reanimation spell from grishoalbrand sure. Decks like elves will bury you by t3 easily. Neither of those are tier decks, and those tier decks routinely carve through weaker decks in larger tournaments.
Imho budget for modern is a much higher bar than people give it credit for.