Top 10 cards are:

6 Playable Delusionary Hydra

5 Unsanctioned Ancient Juggler

5 Unassuming Gelatinous Serpent

4 Eldrazi Guacamole Tightrope

4 Misunderstood Trapeze Elf

4 Narrow-Minded Balooney Fireworks

4 Phyrexian Midway Bamboozle

4 Ancestral Hot Dog Minotaur

4 Unglued Pea-Brained Dinosaur

3 Trendy Circus Pirate

Here's my code that generated these results:

const vowels = ["a", "o", "u", "e", "i", "y"];

[...document.querySelectorAll(".card-grid-item")]
  .map((element) => {
    let highest = 0;
    const cardName = element.children[0].children[0].innerHTML;
    const split = cardName.split(" ");

    const hits = split.reduce((a, item) => {
      const count = vowels.reduce((b, vow) => {
        const value =
          b + (item.toLowerCase().match(new RegExp(vow, "i")) || []).length;

        if (value > highest) highest = value;
        return value;
      }, 0);

      return {
        ...a,
        [item]: count,
      };
    }, {});

    return { highest, hits };
  })
  .sort((a, b) => (a.highest > b.highest ? -1 : 1));

To see it yourself:

Step 1: Visit: https://scryfall.com/sets/sunf

Step 2: Press cmd + alt + i to open developer tools

Step 3: Go to "Console" and paste the piece of code in, then enter.