Well with Beginner to Advanced maps I got 3 medals on first try. Ultimate doesn't really seem that much more RNG heavy, but failed it on first try. With 3 squads in top-middle starting spot, you have 3 squads pass middle RNG node and thus 87.5% chance to kill that pest in the middle between whirlwinds. With 2 squads on the top-left starting spot and non squads from middle dying you then have 4 squads pass top RNG node and thus you have 93.75% chance to kill pest after that node. So technically there is 82.03% chance to 3 medal that map, but RNG can be an asshole. Map is doable with 65-75k power squads assuming you put best two on top-left, use solar blasts, and get average luck with skill activations.
On the screen-cap is the default starting set-up. You can use that to farm dumplings, as they aren't hidden behind RNG. For 3 medals thou I would recommend to move squad from left-middle to top-middle to maximize chances to succeed. And of course don't put Lilac or similar squads in top-middle.